Since the publication of the article Chemistry, in the Encyclopaedia Britannica, that science has been so much extended and improved as to have acquired an entirely new character. And although we have given a full account of a most important branch of this improvement in our article under the head Atomic Theory, it is conceived, that a connected view of the present state of Chemical Philosophy, will add much to the utility of the present work. This we shall endeavour to give in the most condensed form consistent with perspicuity.
Chemistry takes cognizance of all changes in the constitution of matter, whether effected by heat, mixture, or other means. Its general range, therefore, is so extensive, and the individual cases, requiring explanation, so numerous, that Arrangement is of the first consequence to its successful study; and, in the present state of our knowledge, it will be found most convenient to begin with the discussions relating to the general powers or properties of matter, and afterwards to proceed to the examination of individual substances, and to the phenomena which they offer when presented to each other under circumstances favourable to the exertion of their mutual chemical agencies.
The powers and properties of matter, connected with chemical changes, may be considered under the heads of
1. Attraction. 2. Heat. 3. Electricity.
I. Attraction.
Attraction may be regarded as acting at sensible and at insensible distances. In the former case, it is called gravitation. It is the power by which substances are propelled towards the earth; it exists in all known forms of matter, and acts directly as the mass, and inversely as the square of the distance: And, when restrained by inertia, it preserves the planetary bodies in their orbits, presides over their movements, and tends to confer upon the system of the universe that consummate harmony which the genius of Newton has unveiled.
Attraction is also exerted at insensible distances, and among the minutest atoms of matter. It thus preserves the form and modifies the texture of solids, gives a spherical figure to fluids, and influences the mechanical characters of bodies; and, when it operates upon dissimilar particles, it produces their union, giving rise to new and infinitely varied productions.
The results of attraction, as relating to the forms of matter, are influenced by the circumstances under which it has taken place. Sometimes the particles are, as it were, indiscriminately collected; in other cases they are beautifully arranged, giving rise to regular and determinate figures. In this case, bodies of the same composition invariably affect the same form; hence we are often enabled to infer the composition of a substance from accurate inspection of its external or mechanical characters. The regular polyhedral solids thus resulting from the influence of attraction upon certain kinds of matter, are usually called crystals, and the bodies are said to be susceptible of crystallization. To enable the particles of bodies to assume that regular form which crystals exhibit, it is obvious, that they must have freedom of motion, and, accordingly, the first step towards obtaining a body in its crystalline form, is to confer upon it either the liquid or aciform state. The former is usually effected by solution in water; the latter by exposure to heat. When common salt is dissolved in water, its particles may be regarded as disposed at regular distances throughout the fluid; and if the quantity of water be considerable, the particles will be too far asunder to exert reciprocal attraction; in other words, they will be more powerfully attracted by the water than by each other. If we now slowly get rid of a portion of the water by evaporation, the saline particles will gradually approach each other, and they will aggregate according to certain laws, producing a regular solid of a cubic form. The regularity of this figure will be influenced by the rapidity of the evaporation; if the process be slowly conducted, the particles unite with great regularity; if hurried, the crystals are irregular and confused. In common cases, the evaporation may be continued till a pellicle forms upon the surface of the solution, which indicates, that the attraction of the saline particles for each other, is becoming superior to their attraction for the water. The formation, therefore, of a superficial pellicle is the common criterion of the fitness of a solution for crystallization; but where the object is to obtain very regular and very large crystals, the evaporation must be much slower, and carried to much less extent; even spontaneous evaporation, or that which takes place at common temperatures, must be resorted to. There are certain bodies which may be dissolved or liquified by heat, and, during slow cooling, may be made to crystallize. This is the case with many of the metals, and with sulphur. Some other substances, when heated, readily assume the state of vapour, and, during condensation, present regular crystalline forms, such as iodine, benzoic acid, camphor, &c. The hardness, brilliancy, and transparency of crystals, often depend upon their containing water, which sometimes exists in large quantities. Thus, sulphate of soda, in the state of crystals, contains more than half its weight. This is called water of crystallization. Some salts part with it by simple exposure to a dry air, when they are said to effloresce; but there are other salts which deliquesce, or attract water from the atmosphere.
Crystallization is accelerated, by introducing into the solution a nucleus, or solid body, upon which the process begins; and manufacturers often avail themselves of this circumstance. Thus we see sugar-candy crystallized upon strings, and verdigris upon sticks. There are cases in which it is particularly advantageous to put a few crystals of the dissolved salt into the solution, which soon cause a crop of fresh crystals; and in some instances, if there be two salts in solution, that will most readily separate, of which the crystals have been introduced. A strong saline solution, excluded from the air, will frequently crystallize the instant that air is admitted,—a circumstance referred to atmospheric pressure. In other cases, agitation produces the same effect.
These phenomena seem connected with the doctrine of latent heat. The presence of light also influences the process of crystallization. Thus we see the crystals collected in camphor bottles in druggists' windows always most copious upon the surface exposed to light; and if we set a solution of nitre in a room which has the light admitted only through a small hole in the window-shutter, crystals will form most abundantly upon the side of the basin exposed to the aperture through which the light enters.
We may now proceed to examine the structure of crystallized bodies, upon which the Theories of Crystallization are founded. This inquiry exposes the connecting link between Chemical and Mechanical properties of bodies.
It is commonly observed, that crystallized bodies affect one form in preference to others. The fluor spar of Derbyshire crystallizes in cubes: so does common salt. Nitre assumes the form of a six-sided prism, and sulphate of magnesia that of a four-sided prism. These forms are liable to vary. Fluor spar and salt crystallize sometimes in the form of octoedra, and there are so many forms of carbonate of lime, that it is difficult to select that which most commonly occurs.
Romé de Lisle referred these variations of form to certain truncations of an invariable primitive nucleus; and Gahn afterwards observed, that when a piece of calcareous spar was carefully broken, all its particles were of a rhomboidal figure. This induced Bergman to suspect the existence of a primitive nucleus in all crystallized bodies. When Häyi* entered this field of inquiry, he not only corroborated the opinions of Bergman, and submitted former hypotheses to experimental proof, but traced with much success the laws of crystallization, and pointed out the modes of transition from primitive to secondary figures.
Those who are in the habit of cutting and polishing certain gems, have long known that they only afford smooth surfaces when broken in one direction; and that in others the fracture is irregular and uneven. This is the case with crystallized bodies in general. If we attempt to split a cube of fluor spar with the blade of a knife, assisted by a hammer, we shall find that it will only yield kindly in the direction of the solid angles; and pursuing the division in these directions, an octoedron will be the resulting figure, as in this diagram.
In splitting a six-sided crystal of calcareous spar, we find that, of the six edges of the superior base, three alternate edges only will yield to the blow: those, for instance, marked \(a\), \(b\), \(c\); and the division will take place in a plane inclined at an
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* Traité de Mineralogie. Paris, 1801. The three intermediate edges resist this division. But in dissecting the inferior base of the crystal, the intermediate edges will alone yield, namely \(a\), \(b\), \(c\). If we continue this dissection in the same directions, we shall at length obtain the obtuse rhomboid, which is seen in this diagram in its relative situation to the including prism.
We thus then arrive at the primitive form of the calcareous spar, and from whatever secondary form it has been obtained, it is always a rhomboid, having obtuse angles of 105°. But an obtuse rhomboid is also the primitive form of other bodies, as of pearl spar, iron spar, and tourmalin. But here the inclination of the surface points out a difference. Thus the primitive angle of pearl spar is 106° 5', of iron spar 107°,* and of tourmalin 113° 10'.
These instances show the necessity of being provided with instruments for measuring the angles of crystals with nice accuracy; they are termed goniometers. The reflective goniometer, invented by Dr Wollaston,† is the most useful of these instruments. It enables us to determine the angles even of minute crystals with great accuracy; a ray of light reflected from the surface of the crystal being employed as radius, instead of the surface itself.
In following the method above described, having obtained six primitive forms,
1. The cube, parallelopipedon, &c. 2. The tetraëdron. 3. The octoëdron. 4. The hexangular prism. 5. The rhombic dodecaëdron. 6. The dodecaëdron with triangular faces.
These primitive forms, by further mechanical analysis, may be reduced to three integral elements.
1. The parallelopiped, or simplest solid, having six surfaces parallel, two and two. 2. The triangular, or simplest prism, bounded by five surfaces. 3. The tetraëdron, or simplest pyramid, bounded by four surfaces.
The secondary forms are supposed to arise from decrements of particles taking place on different edges and angles of the primitive forms. Thus a cube, having a series of decreasing layers of cubic particles upon each of its six faces, will become a dodecaëdron, if the decrement be upon the edges; but an octoëdron, if upon the angles; and by irregular intermediate and mixed decrements, an infinite variety of secondary forms would ensue.
But in crystallography we meet with appearances which Hauy's theory but imperfectly explains. A slice of Derbyshire spar, for instance, obtained by making two successive and parallel sections, may be divided into acute rhomboids; but these are not the primitive form of the spar, because, by the removal of a tetraëdron from each extremity of the rhomboid an octoëdron is obtained. Thus, as the whole mass of fluor may be divided into tetraëdra and octoëdra, it becomes a question which of these forms is to be called primitive, especially as neither of them can fill space without leaving vacuities, nor can they produce any arrangement sufficiently stable to form the basis of a permanent crystal. To obviate this incongruity, Dr Wollaston‡ has very ingeniously proposed to consider the primitive particles as spheres which, by mutual attraction, have assumed that arrangement which brings them as near as possible to each other. When a number of similar balls are pressed together in the same plane, they form equilateral triangles with each other; and if balls so placed were cemented together and afterwards broken asunder, the straight lines in which they would be disposed to separate, would form angles of 60° with each other. A single ball, placed anywhere on this stratum, would touch three of the lower balls, and the planes touching their surfaces would then include a regular tetraëdron. A square of four balls, with a single ball resting upon the centre of each surface, would form an octoëdron, and upon applying two other balls at opposite sides of this octoëdron, the group will represent the acute rhomboid. Thus the difficulty of the primitive form of fluor, above alluded to, is done away, by assuming a sphere as the ultimate molicula. By oblate and oblong spheroids other forms may be obtained. The subject of crystallization has more lately engaged the attention of Mr J. F. Daniell,|| and his researches have produced some singular confirmations of Dr Wollaston's hypothesis. If an amorphous piece of alum be immersed in water, and left quietly to dissolve, at the end of about three weeks we shall observe that it has been unequally acted upon by the fluid: the mass will present the forms of octoëdra, and sections of octoëdra, as it were carved or stamped upon its surface, as seen in these figures:
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* Wollaston. Phil. Trans. 1812. † Phil. Trans. 1809. ‡ Phil. Trans. 1813. Some acute remarks on the formation of crystals may be found in Hooke's Micrographia. || Quarterly Journal of Science and the Arts, Vol. I. Chemistry. This appearance is produced when the attraction of the water for the solid is nearly counterbalanced by its mechanical texture. The crystals produced by this species of dissection, are highly curious from their modifications and relative positions, as the same group present the primitive form as well as its truncations and decrements. Other salts yield other figures, and by more complicated chemical action, as of acids upon carbonate of lime, the metals, &c. analogous results are obtained. Here, then, instead of dividing a crystal by mechanical force, its structure is gradually developed by the process of solution. In these cases two circumstances are particularly remarkable: the crystals are different, and their forms vary with the different faces of the original mass. In one direction we observe octoëdra and sections of octoëdra; in another, parallelograms of every dimension, modified with certain determinate intersections.
If, in either of these positions, we turn the mass upon its axis, the same figures will be perceived at every quadrant of a circle; and, if we suppose the planes continued, they will mutually intersect each other, and various geometrical solids will be constructed. In this way, alum alone furnishes octoëdrons, tetraëdrons, cubes, four and eight-sided prisms, either with plain or pyramidal terminations, and rhombic parallelopipeds. It is evident, then, that no theory of crystallization can be admitted, which is not founded upon such a disposition of constituent particles, as may furnish all these modifications, by mere abstraction of certain individuals from the congeries, without altering the original relative position of those which remain; and these conditions may be fulfilled by such an arrangement of spherical particles, as would arise from the combination of an indefinite number of balls ended with mutual attraction, and no other geometrical solid is adequate to the purpose; and where bodies furnish crystals differing from the octoëdral series, an analogous explanation is furnished, by supposing their constituent particles to consist of oblate spheroids, whose axes bear different proportions to each other in different substances. Hence we may also conclude, that the internal structure of all crystals of the same body is alike, however the external shapes differ. In corroboration of the above hypothesis, we may remark, that the hexaëdron is, of all geometrical figures, that which includes the greatest capacity under the least surface. If, therefore, the ultimate particles of crystalline bodies be spheres or spheroids, the greatest possible number in the least space will be included in this form. It is probable that the exterior shape of every crystal is determined by the nucleus first formed by a certain definite number of particles, which, by the power of mutual attraction, overcome the resistance of the medium in which they were suspended, or from which they were separated. This number may vary with the solvent, or other contingent circumstances. Four spherical particles, thus united, would balance each other in a tetraëdral group, six in an octoëdral group, and each would present particular points of attraction to which all subsequent deposits would be directed. Now, let us imagine two nuclei formed in the same solution, whose axes run in contrary directions; their increase will consequently be in contrary directions, and each will attract a particular system of particles from the surrounding medium. If these two systems should cross each other in their course, a greater number will be brought within the sphere of mutual reaction at the point of junction, and they ought to arrange themselves in the least possible compass. The facts here answer to the theory. If we select any crystals, having others crossing them nearly at right angles, and separate them, the points of junction invariably present an hexaëdral arrangement.
In connection with chemistry, the theory of crystallization opens a new avenue to the science, and frequently enables us to ascertain directly that which, independent of such aids, could only be arrived at by an indirect and circuitous route. We frequently read the chemical nature of substances in their mechanical forms. To the mineralogist, an intimate acquaintance with the crystalline forms and modifications of natural bodies is essentially requisite. Indeed, the theory of crystallization may be considered as one of the great supports of that useful branch of natural history, and it is to the indefatigable exertions of Haüy that much of its present perfection is to be referred. In the arts, the process of crystallization is turned to very valuable account, in the separation and purification of a variety of substances.
We have hitherto considered Attraction as disposing the particles of bodies to adhere, so as to form Affinity masses or aggregates, and, in many instances, to arrange themselves according to peculiar laws, and to assume regular geometrical figures. We are now to regard this power as operating upon dissimilar particles, as presiding over the composition of bodies, and as producing their chemical varieties. This is Chemical Attraction or Affinity. If, into a glass vessel, exhausted of air, be introduced some sulphur, and copper filings, and heat be applied so as to melt the former, it will presently combine with the latter. We observe, as the results of this attraction between the sulphur and copper, 1. That the substance produced has not the intermediate properties of its elements, but that it presents new characters. 2. That much heat and light are evolved during the Chemistry. mutual action. 3. That sulphur and copper will unite in certain proportions only. In liquids and gases, similar changes of properties may be exhibited, and, in many cases, a change of form or state results. Thus the combination of aeriform bodies produces a solid, as when muriatic and ammoniacal gases produce the solid salt called muriate of ammonia. Solids also produce liquids, and liquids gases. In all cases of true chemical combination, the properties of the compound differ essentially from those of its component parts, and a series of new bodies, possessed of distinct and peculiar characters, are produced. Such operations are not confined to art. Nature presents them on an extended scale, and, in connection with the functions of life, renders them subservient to the most exalted purposes.
The new chemical powers, therefore, that bodies acquire in consequence of combination, are often extremely remarkable, and can only be learned by experiment. It frequently happens that inert bodies produce inert compounds, and that active substances remain active when combined; but the reverse often occurs. Thus oxygen, sulphur, and water, in themselves tasteless and comparatively inert, produce oil of vitriol when chemically combined; and potash, which is a powerful caustic when combined with oil of vitriol, forms a salt possessed of little activity. As chemical action takes place among the ultimate or constituent elements of bodies, it must obviously be opposed by the cohesion of their particles, and chemical attraction is often prevented by mechanical aggregation. A piece of the metal antimony, put into the gas called chlorine, is only slowly and superficially acted upon; but if the mechanical aggregation be previously diminished, by reducing the metal to powder, it in that state rapidly unites with the gas, and burns the instant that it is introduced. Heat increases the chemical energies of bodies. Its effects are sometimes only referable to the diminution of adhesion by expansion, but in other cases are peculiar and complicated, as will be shown under the sections on Heat and Electricity.
Bodies are possessed of very different attractive powers, and if several be brought together, those which have the strongest mutual affinities enter first into union. Thus, if nitric acid be poured upon a mixture of lime and magnesia, it dissolves the former in preference to the latter earth. The knowledge of this fact enables us to separate bodies when united, or to perform the process of decomposition. Thus, if I add an aqueous solution of lime to a solution of magnesia in nitric acid, the latter earth is thrown down or precipitated, and the lime occupies its place in the acid.
Decomposition is effected under a variety of circumstances, and by many methods; but it is commonly described by chemists as Simple and Complex, or Single and Double.
In cases of simple attraction or affinity, one body separates another from its combination with a third. Thus, when potash is added to a solution of sulphate of zinc (composed of sulphuric acid and oxide of zinc), the oxide of zinc is separated, and sulphate of potash is produced.
In cases of double decomposition, two new compounds are produced; as when a solution of nitrat of barytes is mixed with solution of sulphate of soda, the results are a precipitate of sulphate of barytes, and a solution of nitrat of soda.
It is obvious, from the uniform results of chemical action, that affinity must be governed by certain definite laws, by which its results are determined, and upon which its uniformity depends. Attention was first called to this subject by Mr Higgins in 1789.* He conceived that chemical attraction only prevailed between the ultimate particles of simple elementary matter and between compound atoms; and, in applying this idea to chemical theory, he expressed by numbers the relative forces of attraction subsisting between the different kinds of ultimate particles and atoms of matter.
These views were subsequently extended and improved by Mr Dalton,† and have since engaged the attention of some most eminent chemical philosophers; among whom we may enumerate Gay Lussac and Berzelius, Davy, Wollaston, and Thomson.
The atomic doctrine, or theory of definite proportions, has been much blended with hypothetical views; but it will be most satisfactorily and usefully considered as an independent collection of facts.
When bodies unite so as to form one compound only, that compound, under whatever circumstances it is produced, whether by nature or art, always contains the same relative proportions of its components; and where two bodies unite in more than one proportion, the second, third, &c. proportions are multiples or divisions of the first. This law is well exhibited in the combinations of gaseous bodies. These are seen to unite in simple ratios of volume. Water is composed of hydrogen and oxygen, and 1 part by weight of the former gas, unites to 7.5 of the latter. The specific gravity of hydrogen, compared with that of oxygen, is as 1 to 15: it is obvious, therefore, that one volume of hydrogen unites to half a volume of oxygen, and that the composition of water will be represented by weight and volume thus:
\[ \begin{array}{|c|c|} \hline I. & 7.5 \\ O. & H. \\ \hline \end{array} \]
Muriatic acid gas consists of 1 part by weight of hydrogen, and 33.5 by weight of chlorine. The relative specific gravities of these gases are as 1 to 33.5. It is obvious, therefore, that they combine in equal volumes, and that muriatic acid gas may be thus represented.
\[ \begin{array}{|c|c|} \hline I. & 33.5 \\ H. & C. \\ \hline \end{array} \]
* A Comparative View of the Phlogistic and Antiphlogistic Theories, &c. London, 1789. † New System of Chemical Philosophy. Manchester, 1810. Carbonic acid unites to potash in two proportions, and forms two definite compounds. In the one, 70 parts of potash are combined with 30 of carbonic acid; in the other, 70 of potash are united to 60 of carbonic acid. Lead combines with oxygen in three proportions; the first compound consists of 100 lead + 8 oxygen, the second of 100 + 12, the third of 100 + 16.
Bodies are always obedient to these laws of union; and, in whatever way they are produced, their component parts exist in the same relative proportions.
HEAT.
Heat may be considered as a power opposed to Attraction, for it tends to separate the particles of bodies; and whenever a body is heated, it is also expanded. Expansion is the most obvious and familiar effect of heat; and it takes place, though in different degrees, in all forms of matter. Solids are the least expandible,—liquids expand more readily than solids,—and gases or aeriform bodies more than liquids. When a body has been expanded by heat, it regains its former dimensions when cooled to its former temperature. Different bodies expand differently when equally heated. The metals are the most expansible solids; but among them, zinc expands more than iron, and iron more than gold. Liquids differ also in their relative expansibilities. Ether is more expansible than spirit of wine, and spirit more than water, and water more than mercury. Those liquids are generally most expansible which boil at the lowest temperature. In all pure gaseous bodies, the rate of expansion for similar increase of temperature is similar: 100 measures of air, when heated from the freezing to the boiling point of water, suffer an increase in bulk = 37.5 parts at mean pressure. As heat increases the bulk of all bodies, it is obvious that change of temperature is constantly producing changes in their density or specific gravity, as may be easily demonstrated in fluids where there is freedom of motion among the particles. If I apply heat to the bottom of a vessel of water, the heated part expands and rises, while a cold or denser stratum occupies its place. In air, similar currents are continually produced, and the vibratory motion observed over chimney pots, and slated roofs which have been heated by the sun, depends upon this circumstance. The warm air rises, and its refracting power being less than that of the circumambient colder air, the currents are rendered visible by the distortion of objects viewed through them. There is only one strict exception to the general law of expansion by heat, and contraction by cold; this is in the case of water, which expands considerably when it approaches its freezing point.
If we mix equal quantities of the same fluid at different temperatures, the cold portion will expand as much as the hot portion contracts, and the resulting temperature is the mean; so that it appears, that as much heat as is lost by the one portion is gained by the other. Upon this principle, thermometers are constructed. A common thermometer consists of a tube terminated at one end by a bulb, and closed at the other. The bulb and part of the tube are filled with a proper liquid, generally mercury, and a scale is applied, graduated into equal parts. Wherever this instrument is applied to bodies of the same temperature, the mercury, being similarly expanded, indicates the same degree of heat. In dividing the scale of a thermometer, the two fixed points usually resorted to are the freezing and boiling of water, which always take place at the same temperature, when under the same atmospheric pressure. The intermediate part of the scale is divided into any convenient number of degrees; and it is obvious, that all thermometers thus constructed will indicate the same degree of heat when exposed to the same temperature. In the centigrade thermometer, this space is divided into 100°; the freezing of water being marked 0, the boiling point 100°. In this country we use Fahrenheit's scale, of which the 0° is placed at 32° below the freezing of water; which, therefore, is marked 32°, and the boiling point 212°, the intermediate space being divided into 180°. Another scale is Reaumur's; the freezing point is 0°, the boiling point = 80°. These are the principal thermometers used in Europe. Each degree of Fahrenheit's scale is equal to $\frac{5}{9}$ of a degree on Reaumur's; if, therefore, the number of degrees on Fahrenheit's scale, above or below the freezing of water, be multiplied by 4, and divided by 9, the quotient will be the corresponding degree of Reaumur.
| Fahrenheit | Reaumur | |------------|---------| | 68° - 32° = 36 × 4 = 144 ÷ 9 = 16° | 36° + 32° = 68 | | 212° - 32° = 180 × 4 = 720 ÷ 9 = 80° | |
To reduce the degrees of Reaumur to those of Fahrenheit, they are to be multiplied by 9, and divided by 4.
| Reaumur | Fahrenheit | |---------|------------| | 16° × 9 = 144 ÷ 4 = 36° + 32° = 68 | 36° + 32° = 68 | | 80 × 9 = 720 ÷ 4 = 180 + 32 = 212° | |
Every degree of Fahrenheit is equal to $\frac{5}{9}$ of a degree on the Centigrade scale; the reduction, therefore, is as follows.
| Fahrenheit | Centigrade | |------------|------------| | 212° - 32° = 180 × 5 = 900 ÷ 9 = 100° | 100° | | Centigrade | Fahrenheit | | 100 × 9 = 900 ÷ 5 = 180 + 32 = 212° | |
Where a thermometer is intended to measure very low temperatures, spirit of wine is employed in its construction, so that fluid has never been frozen, whereas the low temperature at which it boils, renders it unfit for measuring high temperatures. Quicksilver will indicate 500°, but freezes at —40°. Air is sometimes resorted to as indicating very small changes of temperature; and of air thermometers, that described by Professor Leslie, under the name of the Differential Thermometer, is the best. It consists of two large glass bulbs containing air, united by a tube twice bent at right angles, containing coloured sulphuric acid. When a hot body approaches one of the bulbs, it drives the fluid towards the other. The great advantage of this instrument in delicate experiments is, that general changes of the atmosphere's temperature do not affect it, but it only indicates the difference of temperature between the two balls.
The relative quantities of heat which different bodies in the same state require to raise them to the same thermometric temperature, is called their specific heat, and those bodies which require most heat are said to have the greatest capacity for heat. That the quantity of heat in different bodies of the same temperature is different, was first shown by Dr Black, in his lectures at Glasgow, in 1762.
It has been stated as a proof of the accuracy of the thermometer, that equal volumes of the same fluid, at different temperatures, give the arithmetical mean, or mixture. Thus, the temperature of a pint of hot and a pint of cold water is, after mixture, as near as possible half-way between the extremes. The cold water being of a temperature of $50^\circ$, and the hot of $100^\circ$, the mixture raises the thermometer to $75^\circ$. But if a pint of quicksilver at $100^\circ$ be mixed with a pint of water at $50^\circ$, the resulting temperature is not $75^\circ$, but $70^\circ$; so that the quicksilver has lost $30^\circ$, whereas the water has only gained $20^\circ$. Hence, it appears, that the capacity of mercury for heat is less than that of water; and if the weight of the two bodies be compared, which are as $13:3$ to $1$, their capacities will be to each other as $19$ to $1$.
In cases where the specific heat of bodies is to be ascertained, it is convenient that water should be the standard of comparison, or $=1$. The following is a general formula for determining the specific heat of bodies, from the temperature resulting from the mixture of two bodies at unequal temperatures, whatever be their respective qualities. Multiply the weight of the water by the difference between its original temperature, and that of the mixture. Also, multiply the weight of the other liquid, by the difference between its temperature and that of the mixture; divide the first product by the second, and the quotient will express the specific heat of the other substance, that of water being $=1$. Thus, 20 ounces of water at $105^\circ$, mixed with 12 ounces of spermaceti oil at $40^\circ$, produce a temperature of $90^\circ$. Therefore, multiply 20 by 15 (the difference between $105$ and $90$) $= 300$. And multiply 12 by 50 (the difference between $40$ and $90$) $= 600$. Then $300 \div 600 = \frac{1}{2}$, which is the specific heat of oil; that is, water being $1$, oil is $0.5$.
The capacities of bodies for heat have considerable influence upon the rate at which they are heated and cooled. Those bodies which are most slowly heated and cooled have generally the greatest capacity for heat. Thus, if equal quantities of water and quicksilver be placed at equal distances before the fire, the quicksilver will be more rapidly heated than the water, and the metal will cool most rapidly when carried to a cold place. Upon this principle, Professor Leslie ingeniously determined the specific heat of bodies, observing their relative times of cooling a certain number of degrees, comparatively with water, under similar circumstances.
The Calorimeter, invented by Lavoisier for determining the specific heat of bodies, is an inaccurate instrument.
The capacity of gases and vapours differs with the nature of the gas, and with its density. In gases dilatation produces cold, and compression excites heat. A thermometer suspended in the receiver of the air-pump sinks during exhaustion, and sudden compression of air produces heat sufficient to inflame tinder. In liquids, too, condensation diminishes capacity for heat; hence the mixture of spirit and water, and of oil of vitriol and water, evolves heat. The increased capacity which air acquires by rarefaction has its influence in modifying natural temperatures. The air, becoming rarer as it ascends, absorbs its own heat, and hence becomes cold in proportion as it recedes from the earth's surface: thus moisture, rain, or snow, are thrown down on the mountain tops.
When different bodies are exposed to the same source of heat, they suffer it to pass through them with very different degrees of velocity, or they have various conducting powers in regard to heat. Among solid bodies, metals are the best conductors. And silver, gold, and copper, are better conductors than platinum, iron, and lead. Next to the metals, we may, perhaps, place the diamond,—then glass,—then siliceous and hard stony bodies in general,— then soft and porous earthy bodies, and wood,—and, lastly, down, feathers, wool, and other porous articles of clothing.
Liquids and gases are very imperfect conductors of heat, and heat is generally distributed through them by a change of specific gravity, as before stated.
If we apply heat to the upper surface of any fluid, it will with great difficulty make its way downwards. Count Rumford considered fluids as non-conductors of heat; but the more accurate researches of Dalton, Hope, Murray,* and Thomson,† have demonstrated that they do conduct, though very imperfectly. Experiments on the conducting power of air are complex and difficult, and the results hitherto ob- tained are unsatisfactory. They are interfered with by several circumstances presently to be noticed.
The different conducting powers of bodies is shown in the application of wooden handles to metal- lic vessels, or a stratum of ivory or wood is inter- posed between the hot vessel and the metal handle. The transfer of heat is thus prevented. Heat is con- fined by bad conductors; hence clothing for cold climates consists of woollen materials; hence, too, the walls of furnaces are composed of clay and sand. Confined air is a very bad conductor of heat; hence the advantage of double doors to furnaces, to pre- vent the escape of heat, and of a double wall, with an interposed stratum of air, to an ice house, which prevents the influx of heat from without. From the different conducting powers of bodies in respect to heat, arise the sensations of heat and cold expe- rienced upon their application to our organs, though their thermometric temperature is similar. Good conductors occasion when touched a greater sensa- tion of heat and cold than bad ones. Metal feels cold because it readily carries off the heat of the body; and we cannot touch a piece of metal im- mersed in air of a temperature moderate to our sense.
Heat has great influence on the forms or states of bodies. When we heat a solid, it becomes fluid or gaseous; and liquids are converted into aërial form bodies or vapours. Dr Black investigated this effect of heat with singular felicity, and his researches rank among the most admirable effects of experimental philosophy.‡ During the liquefaction of bodies, a quantity of heat is absorbed, which is essential to the state of fluidity, and which does not increase the sensible or thermometric temperature. Conseque- ntly, if a cold solid body, and the same body hot and in a liquid state, be mixed in known proportions, the temperature after mixture will not be the propor- tional mean, as would be the case if both were liquid, but will fall short of it; much of the heat of the hotter body being consumed in rendering the colder solid liquid, before it produces any effect upon its sensible temperature. Equal parts of water at 32° and of water at 212° will produce on mixture a mean tem- perature of 152°. But equal parts of ice at 32° and Chemistry. of water at 212° will only produce (after the lique- faction of the ice) a temperature of 52°, the greater portion of the heat of the water being employed in thawing the ice, before it can produce any rise of temperature in the mixture. To heat thus insensible or combined, Dr Black applied the term latent heat. The actual loss of thermometric heat in these cases was thus estimated: a pound of ice at 32° was put into a pound of water at 179°; the ice melted, and the temperature of the mixture was 32°. Here the water was cooled 140°, while the temperature of ice was unaltered; that is, 140° of heat disappeared,— their effect being not to increase temperature, but to increase fluidity.
The same phenomena are observable in all cases of liquefaction, and we produce artificial cold, often of great intensity, by the rapid solution of certain saline bodies in water. When fluids are converted into solids, their latent heat becomes sensible; con- gelation therefore is to surrounding bodies a heating process, and liquefaction a cooling process.
When liquids are heated, they acquire the gaseous form, and become invisible elastic fluids, possessed of the mechanical properties of common air. They re- tain this form or state, as long as their temperature re- mains sufficiently high, but reassume the solid form when cooled again. Different fluids pass into the aëri- form state at different temperatures, or their boiling points are different; they are also regulated by the density of the atmosphere. If we diminish atmospher- ic pressure, we lower the boiling point. When the barometer is at 28 inches, water will boil at a lower temperature than when it is at 31 inches. Water under mean atmospheric pressure boils at 212°. At the top of Mont Blanc, Saussure found that it boiled at 187°, so that the heights of mountains, and even of buildings, may be calculated by reference to the temperature at which water boils upon their sum- mits. The Reverend Mr Wollaston has lately de- scribed to the Royal Society, the method of con- structing a thermometer of extreme delicacy, ap- plicable to these purposes. In the vacuum of an air-pump, fluids boil at temperatures considerably below their ordinary boiling points.
The conversion of a liquid into vapour, is always attended with great loss of thermometric heat, and, as liquids may be regarded as compounds of solids and heat, so vapours may be considered as consist- ing of a similar combination of heat with liquids; in other words, a great quantity of heat becomes latent during the formation of vapour. This is easily il- lustrated by immersing a thermometer into a vessel of water placed over a lamp. The quicksilver rises to 212°, the water then boils, and although the source of heat remains, neither the water nor the steam acquire a higher temperature than 212°; the heat then becomes latent, and is consumed in the formation of steam.
* System of Chemistry, Vol. I. † System of Chemistry, Vol. I. ‡ Black's Lectures, edited by John Robison, LL.D. Edinburgh, 1803. To ascertain the absolute loss of thermometric heat in this case, Dr Black* instituted the following experiments: He noted the time required to raise a certain quantity of water to its boiling point; he then kept up the same heat till the whole was evaporated, and marked the time consumed by the whole process; it was thus computed to what height the temperature would have risen, supposing the rise to have gone on above $212^\circ$, in the same ratio as below it, and as the temperature of the steam was the same as that of the water, it was fairly inferred that all the heat above $212^\circ$ was essential to the constitution of aqueous vapour. Dr Black estimated this quantity at about $810^\circ$, that is, the same quantity of heat which is required for the total evaporation of boiling water at $212^\circ$ would be sufficient to raise the water $810^\circ$ above its boiling point, or to $1022^\circ$ had it continued in the liquid state. There are other means of ascertaining the latent heat of steam, which lead us to place it between $900^\circ$ and $1000^\circ$.
When steam is again condensed, or when vapours reassume the liquid state, their latent heat becomes sensible, and in this way it is obvious that a small quantity of steam will, during its condensation, communicate heat sufficient to boil a large quantity of water.
The cold produced by evaporation is, under certain circumstances, very great. Spirit of wine and ether, which readily evaporate, produce considerable cold during that process. Upon this principle, wine coolers and similar porous vessels, refrigerate the fluids they contain; and thus, by accelerating the evaporation of water, by exposing it under an exhausted receiver, containing bodies that quickly absorb its vapour, Professor Leslie has contrived to effect its congelation; the heat required for the conversion of one portion of the water into vapour being taken from the other portion, which is thus reduced to ice.
The heat given off by steam during its condensation, is often advantageously applied to warming buildings, and is at once safe, salubrious, and economical. In many natural operations the conversion of water into vapour, and the condensation of vapour in the form of dew and rain, is a process of the utmost importance, and tends considerably to the equalization of temperature over the globe.
Nothing is known of the nature or cause of heat. It has been by some considered as a peculiar fluid, to which the term Caloric has been applied; and many phenomena are in favour of the existence of such a fluid. By others, the phenomena above described have been referred to a vibratory motion of the particles of matter, varying in velocity with the perceived intensity of the heat. In fluids and gases the particles are conceived to have a motion round their own axis. Temperature, therefore, would increase with the velocity of the vibrations, and increase of capacity would be produced by the motion being performed in greater space. The loss of temperature during the change of solids into liquids and gases, would depend upon loss of vibratory motion, in consequence of the acquired rotatory motion.
Upon the other hypothesis, temperature is referred to the quantity of caloric present; and the loss of temperature which happens when bodies change their state, depends upon the chemical combination of the caloric with the solid in the case of liquefaction, and with the liquid in the case of conversion into the aeriform state.†
**Electricity.**
If a piece of sealing-wax and of dry warm flannel be rubbed against each other, they both become capable of attracting and repelling light bodies. Glass rubbed upon silk exhibits the same phenomena. In these cases the bodies are said to be electrically excited. If two pith-balls be electrified by touching them with the sealing-wax or with the flannel, they repel each other; but if one pith-ball be electrified by the wax and the other by the flannel, they attract each other. The same applies to the glass and silk; it shows a difference in the electricities of the different bodies; and the experiment leads to the conclusion, that bodies similarly electrified repel each other, but that, when dissimilarly electrified, they attract each other.
If one ball be electrified by sealing-wax rubbed by flannel, and another by silk rubbed with glass, those balls will repel each other; which proves, that the electricity of the silk is the same as that of the sealing-wax. But if one ball be electrified by the sealing-wax and the other by the glass, they then attract each other, showing that they are oppositely electrified.
The terms vitreous and resinous electricity were applied to these two phenomena; but Franklin, observing that the same electricity was not inherent in the same body, but that glass sometimes exhibited the same phenomena as wax, and vice versa, adopted another term; and, instead of regarding the phenomena as dependent upon two electric fluids, referred them to the presence of one fluid, in excess in some cases, and in deficiency in others. To represent these states, he used the terms plus and minus, positive and negative. When glass is rubbed with silk, a portion of electricity leaves the silk, and enters the glass. It becomes positive, therefore, and the silk negative; but when sealing-wax is rubbed with flannel, the wax loses and the flannel gains. The former, therefore, is negative, the latter positive. All bodies in nature are thus regarded as containing the electric fluid, and, when its equilibrium is disturbed, they exhibit the phenomena just described.
Very delicate pith-balls, or stripes of gold leaf, are usually employed in ascertaining the presence of electricity; and, by the way in which their divergence is affected by glass or sealing-wax, the kind or
---
* Lectures, pp. 145, et seq.—Dr Black's Researches on the Latent Heat of Steam, led Mr Watt to his great improvement of the steam-engine, of which an account is given in the Lectures, page 184.
† See Davy's Elements of Chemical Philosophy. state of electricity is judged of. When properly suspended or mounted for delicate experiments, they form an electrometer. A considerable improvement in the insulation of the gold leaves has been introduced by the late Mr Singer, and is described in his *Elements of Electricity*. London, 1814.
Some bodies suffer electricity to pass through their substance, and are called conductors. Others only receive it upon the spot touched, and are called nonconductors. The former do not, in general, become electric by friction, and are called nonelectrics. The latter, on the contrary, are electrics, or acquire electricity by friction. They are also called insulators. The metals are all conductors; glass, sulphur, and resins, are nonconductors. Water, damp wood, spirit of wine, and some oils, are imperfect conductors.
There are many substances which show signs of electricity when heated, as the tourmalin, topaz, diamond, boracite, &c.; and in these bodies the different surfaces exhibit different electrical states. Whenever one part of a body, or system of bodies, is positive, another part is invariably negative; and these opposite electrical states are always such as exactly to neutralize each other. Thus, in the common electrical machine, one conductor receives the electricity of the glass cylinder, and the other that of the silk rubber, and the former conductor is positive and the latter negative; but if they be connected, all electrical phenomena cease.
If an insulated conductor be electrified, and an uninsulated conductor be opposed to it, there being between the two a thin stratum of air, glass, or other nonconductor, the uninsulated conductor, under such circumstances, acquires an opposite electrical state to that of the originally electrified insulated conductor. In this case, the uninsulated body is said to be electrified by induction; and the induced electricity remains evident, until an explosion, spark, or discharge happens, when the opposite electricities annihilate each other. Induced electricity may thus be exhibited through a long series of insulated conductors, provided the last of the series be communicated with the earth.
Thus, in the following diagram, A may represent the positive conductor of the electrical machine. B, C, and D, three insulated conductors, placed at a little distance from each other. D having a chain touching the ground, then the balls 1, being positive, will attract the balls 2, which are rendered negative by induction. Under these circumstances, each of the conductors becomes polar, and the balls 3 are positive, while 4 are negative, 5 positive, 6 negative, &c. The central points of the conductors, B, C, D, are neutral. When these opposite electrical states have arrived at a certain intensity, sparks pass between the different conductors, and the electrical phenomena cease.
Upon the principle of induction it is that the accumulation of electricity in the Leyden phial is effected. It consists of a thin glass jar, coated internally and externally with tinfoil to within a short distance of its mouth. When the inner surface is rendered positive by union with the conductor of the electrical machine, the exterior becomes negative by induction. When the inner and outer surfaces are united by a conductor, all electrical accumulation is annihilated by a spark, and the two opposite states are found to have been precisely equivalent. If one Leyden jar be insulated with its internal surface connected with the positive conductor, another jar may be charged from its exterior coating; and if this second jar be insulated, a third may be charged from its exterior coating, and so on for any number of jars, provided always that the exterior coating of the last jar be connected with the ground. In this case, a polar arrangement, similar to that of the conductors just described, will have been formed, glass being the medium of induction instead of air.
Let CP be the positive conductor of the electrical machine, and a, b, c, three insulated Leyden phials, the outer coating of c being connected with the ground; it is then obvious, that there will be the same polar state as in the conductors just noticed; that the insides of a, b, and c, will be positive, and the outsides negative; and that, consequently, on removing the jars from each other, they will all be similarly charged, and that if the three inner surfaces p, p, p, and the three outer surfaces n, n, n, be united, the whole may be discharged as one jar.
Electricians employ the term quantity to indicate the absolute quantity of electric power in any body, and the term intensity to signify its power of passing through a certain stratum of air or other ill-conducting medium.
If we suppose a charged Leyden phial to furnish a spark when discharged of one inch in length, we should find that another uncharged Leyden phial, the inner and outer coating of which were communicated with those of the former, would, upon the same quantity of electricity being thrown in, reduce the length of the spark to half an inch; here, the quantity of electricity remaining the same, its intensity is diminished by one-half, by its distribution over the larger surface.
There are many other sources of electricity than those just noticed. Whenever bodies change their forms, their electrical states are also altered. Thus the conversion of water into vapour, and the congealation of melted resins and sulphur, are processes in which electricity is also rendered sensible.
When an insulated plate of zinc is brought into contact with one of copper or silver, it is found, Chemistry, after removal, to be positively electrical, and the silver or copper is left in the opposite state. If the nerve of a recently killed frog be attached to a silver probe, and a piece of zinc be brought into the contact of the muscular parts of the animal, violent convulsions are produced every time the metals thus connected are made to touch each other.
If a piece of zinc be placed upon the tongue, and a piece of silver under it, a peculiar sensation will be perceived every time the two metals are made to touch.
In these cases the chemical properties of the metals are observed to be affected. If a silver and a zinc wire be put into a wine glass full of dilute sulphuric acid, the zinc wire only will evolve gas; but upon bringing the two wires in contact with each other, the silver will also copiously produce air bubbles.
If a number of alternations be made of copper or silver leaf, zinc leaf, and thin paper, the electricity excited by the contact of the metals will be rendered evident to the common electrometer. Also, if plates of zinc and copper be regularly arranged, with moistened flannel between each pair of plates, we shall observe that, having made 50 or 60 such alternations, the same effect will be produced, and that the zinc plate will give a positive, and the copper extreme a negative charge to the gold leaf electrometer.
If the same arrangement be made with strong brine, or a weak acid, it will be found, on bringing a wire communicating with the last copper plate into contact with the first zinc plate, that a spark is perceptible, and also a slight shock, provided the number of alternations be sufficiently numerous. This is the Voltaic apparatus.
On immersing the wires from the extremes of this apparatus into water, it is found that the fluid suffers decomposition, and that oxygen gas is liberated at the positive wire or pole, and hydrogen gas at the negative pole.
All other substances are decomposed with similar phenomena, the inflammable element being disengaged at the negatively electrical surface; hence it would appear, upon the principle of similarly electrified bodies repelling each other, and dissimilarly electrified bodies attracting each other, that the inherent or natural electrical state of the inflammable substances is positive, for they are attracted by the negative or oppositely electrified pole; while the bodies called supporters of combustion, or acidifying principles, are attracted by the positive pole, and, therefore, may be considered as possessed of the negative power.
All bodies which exert powerful chemical agencies upon each other, when freedom of motion is given to their particles, render each other oppositely electrical when acting as masses. Hence Sir H. Davy, the great and successful investigator of this branch of chemical philosophy, has supposed that electrical and chemical phenomena, though in themselves quite distinct, may be dependent upon one and the same power, acting in the former case upon masses of matter, in the other upon its particles.
We refer to the article Electricity for the theory of the Voltaic Pile; a subject involved in considerable difficulty. In it the quantity of electricity is always increased by extending the surface of the plates, while the intensity rapidly augments with the increase of the number of alternations. Both quantity and intensity, in this instance, are greatly influenced by the chemical action of the fluid upon the plates; the acid bodies, as possessing highly opposite states to those of the metals, are most efficacious; and, in experiments made with the great Voltaic apparatus at the Royal Institution, it has been found that 120 plates, rendered active by a mixture of one part of nitric acid, and three of water, produced effects equal to 480 plates, rendered active by 1 part of nitric acid, and 15 of water.
We have as yet no plausible hypothesis concerning the cause of electrical phenomena, though the subject has engaged the attention of the most eminent philosophers of Europe. They have been by some referred to the presence of a peculiar fluid existing in all matter, and exhibiting itself by the phenomena which have been described, whenever its equilibrium is disturbed, presenting negative and positive electricity when deficient and when redundant. Others have plausibly argued for the presence of two fluids, distinct from each other. Others have considered the effects as referable to peculiar exertions of the attractive powers of matter, and have regarded the existence of any distinct fluid or form of matter to be as unnecessary to the explanation of the phenomena, as it is in the question concerning the cause of gravitation.
When the flame of a candle is placed between a positive and negative surface, it is urged towards the latter; a circumstance which has been explained upon the supposition of a current of electrical matter passing from the positive to the negative pole—indeed, it has been considered as demonstrating the existence of such a current of matter.* But if the flame of phosphorus be substituted for that of a candle, it takes an opposite direction; and, instead of being attracted towards the negative, it bends to the positive surface. It has been shown that inflammable bodies are always attracted by negative surfaces, and acid bodies, and those in which the supporters of combustion prevail are attracted by positive surfaces. Hence the flame of the candle throwing off carbon, is directed to the negative pole, while that of phosphorus goes to the positive, consistently with the ordinary laws of electro-chemical attraction.
There are many experiments which sanction the idea that electricity is "an exhibition of attractive powers acting in certain combinations." If we discharge a Leyden phial through a quire of paper, the perforation is equally burred upon both sides, and not
* Cuthbertson's Practical Electricity and Galvanism, P. 104. London, 1807. upon the negative side only, as would have been the case if any material body had gone through in that direction. The power seems to have come from the centre of the paper, as if one-half of the quire had been attracted by the positive, and the other by the negative surface.
In this outline of the history of the powers of matter, an attempt has been made to draw together, under one point of view, the principal facts required to render the subsequent parts of this article intelligible. It has been necessary, on many occasions, to refer to the more extended discussions in the body of this work; and, under the heads Crystallization, Chemical Affinity, Heat, Electricity, and Galvanism, the reader will find ample materials for the completion of this sketch.
PART II.
Of the substances belonging to our globe, some are of so subtle a nature as to require minute and delicate investigation to demonstrate their existence; they can neither be confined nor submitted to the usual modes of examination, and are known only in their states of motion as acting upon our senses, or as producing changes in the more gross forms of matter. They have been included under the general term of Etherial or Imponderable Matter, which, as it produces different phenomena, must be considered as differing either in its nature or affections. Respecting the nature of these phenomena, two opinions have been entertained, and each ably supported. It has been supposed by Haygens and Descartes, that they arise from vibrations of a rare elastic medium which fills space; while Newton has considered them as resulting from emanations of particles of matter.
The other forms of matter are tangible and ponderable, and, therefore, easily susceptible of accurate examination; they may be considered as resulting from the mutual agencies of heat and attraction, and are comprehended under the three classes of Solids, Liquids, and Gases.
RADIANT MATTER.
In considering the phenomena of radiant matter as connected with chemistry, its mechanical properties must often be necessarily dwelt upon, as importantly connected with the changes it effects in the composition of bodies. These, however, cannot be minutely entered into in this place; they will be found discussed in the body of the work. (See Optics, &c.) Such points of the inquiry will only be alluded to as are absolutely necessary to render the subject intelligible to the Chemist. That a sunbeam, in passing through a dense medium, gives rise to a series of brilliant tints similar to those of the rainbow, was known in the earliest ages, but it required the sagacity of Newton to develop the cause of the phenomenon. He proved, that light consists of rays differing from each other in their relative refrangibilities; and guided by their colour, considered their number as seven:—red, orange, yellow, green, blue, indigo, and violet. Of these rays, the red being least refrangible, falls nearest that spot which the ray would have passed to, had it not been refracted, while the violet ray being most refrangible, is thrown to the greatest distance;—the intermediate rays possess mean degrees of refrangibility. These differently coloured rays are not susceptible of further decomposition, by any number of refractions, but when they are collected into a focus they reproduce white light. Upon these phenomena is founded the Newtonian theory of colours.
If a solar beam be refracted by a prism, and the coloured image received upon a sheet of paper, it will be found, on moving the hand gently through it, that there is an evident increase of temperature towards the red ray. This fact seems to have been first noticed by Dr Hutton (Dissertation on Light and Heat, p. 39); but it is to Dr Herschel (Philos. Trans., 1800) that we are indebted for a full investigation of the subject. If the coloured rays be thrown successively upon delicate thermometers, it will be found, that if the heating power of the violet rays be considered = 16, that of the green rays will be = 26, and of the red = 55. These circumstances suggested the possibility of the heating power of the spectrum extending beyond the red ray; and on applying a thermometer just out of the red ray, and beyond the limits of the visible spectrum, this was found to be the case. A thermometer in the red ray rose 7° in ten minutes, but just beyond the red ray the rise was = 9°. It is evident, therefore, that, independent of the illuminating rays, there are others which produce increase of temperature, and these, from their increase towards the red ray, and from the spot which they principally occupy in the refracted congeries, are possessed of less refrangibility than the visible rays.
That these calorific rays are susceptible of refraction and reflection, is proved by the intense heat produced when the solar rays are concentrated into a focus by a lens, or by a concave mirror.
The radiant matter emitted by terrestrial bodies at high temperatures, agrees in many of its properties with that constituting the solar rays, but in others it presents material differences. The investigation of this subject constitutes a beautiful department of philosophic inquiry. The effect we perceive in approaching a fire chiefly results from radiation; and is little connected with the immediate conducting power of the air; and if a concave metallic mirror be held opposite the fire, a heating and luminous focus will be obtained. The affections of terrestrial radiant matter are best demonstrated by employing two concave mirrors of planished tin or plated copper, placed at a distance of about 10 feet asunder. (Pictet Essais de Physique.) Under these circumstances, when a thermometer is in the focus of one of the mirrors, it will be found sensible to the effects of a heated body placed in the focus of the opposed mirror; and that the effect is produced by reflection, and not by mere direct radiation, is proved, either by drawing the thermometer out of the focus to- Chemistry.
wards the opposed mirror, or by placing a screen between the thermometer and its mirror, when diminution of temperature is in either case indicated.
If the flame of a candle be placed in the focus of one mirror, a heating and luminous focus is obtained from the other; but if a plate of glass be now interposed between the two mirrors, the rays of heat are arrested, while those of light freely passing through the glass, are collected, as usual, in the opposite focus. This, therefore, proves a difference between solar and terrestrial heat; the rays of the former pass through glass without heating it; the rays of the latter are stopped by glass, and it becomes hot when opposed to them. (Scheele's Experiments on Air and Fire.)
In these experiments upon the radiation of terrestrial heat, the temperature excited by the radiant matter appears always relative to that of the heated or radiating body; and if we assume that all bodies are constantly throwing off radiant matter, the effects of temperature which it produced when condensed or collected into a focus by a concave mirror will bear a relation to the source; for the particles may be conceived to move with such velocity as not to be affected by circumjacent bodies, or by the circumambient air. Thus, white hot iron produces a greater effect upon the focal thermometer than that which is only red hot, and red hot iron causes a greater effect than hot water—a body of the same temperature, as the thermometer causes no change in it, but cold bodies produce an effect of cold, because the particles which they radiate, when stopped by impinging upon the thermometer bulb, are of a lower temperature. Radiation has by some been accounted for upon the idea of the heated body producing undulations in the air, something analogous to those waves excited by sonorous bodies; but matter in motion may rather be regarded as the cause of the effect, and the different phenomena of prismatic refraction and of solar and terrestrial radiation can only be explained upon such an hypothesis.
Radiation goes on in all elastic media, and in the Torricellian and air pump vacuum.
It has long been known in regard to solar rays, that their heating effect depends much upon the colour of the surfaces upon which they impinge, and that black and dark bodies are more heated than those which are white or of light tints, circumstances dependent upon absorption and reflection. Professor Leslie has shown that the phenomena of terrestrial radiation are connected with the nature of the radiating surface; and that those surfaces which are the best radiators of this heat, are also gifted with the greatest absorbing power. (Leslie on Heat.)
Unmetallic and unpolished surfaces are the best radiators, and also the best receivers of radiant heat; while polished metallic substances are the worst radiators, and have the lowest absorbing powers. In the experiments with the metallic mirrors, the whole nearly of the heat is reflected, and the mirror itself does not become warm; but if it be coated with any unpolished and especially unmetallic coating, as with paper, or paint, the radiation is then scarcely perceptible, and the mirror becomes hot from the absorption of the radiant matter.
In Professor Leslie's experiments it was found, that a clean metallic surface produced an effect = 12 upon the thermometer. When covered with a thin coat of glue, its radiating power was so far increased as to produce an effect = 80; and, on covering it with lamp-black, it became = 100.
In these cases of radiation the colour of the surface does not interfere, and the different effects must be referred to the mechanical structure of the radiating surface. White paper and lamp-black produce nearly the same effects, and paper coloured blue, red, yellow, and green, does not differ in radiating power from that which is white, provided the colour produces no change of texture in the paper.
The connection of the receptive with the radiating power is made obvious by coating the bulbs of thermometers with different substances. Thus, the effect of radiant heat upon a thermometer bulb covered with a thin coating of lamp-black being = 100; when the bulb is covered with silver-leaf the effect is only = 12.
Radiant matter possesses considerable influence over the chemical energies of bodies. If equal volumes of the gases called chlorine and hydrogen be exposed in a dark room, they slowly combine, and produce muriatic acid gas; but if they be exposed to the direct rays of the sun, the combination is very rapid, and often accompanied by an explosion.
Chlorine and carbonic oxide have scarcely any tendency to combine even at high temperature when light is excluded, but exposed to the solar rays they enter into chemical union. Chlorine has little action upon water, unless exposed to light, and, in that case, the water which consists of oxygen and hydrogen is decomposed. The hydrogen unites with the chlorine to produce muriatic acid, and the oxygen is evolved and combined in a gaseous form.
These, and numerous other similar cases which might be adduced, show that radiant matter influences the chemical energies of bodies, independent of its heating powers. Scheele (Experiments on Air and Fire, p. 78, &c.) was the first who entered upon this curious investigation; and many important facts connected with it have been more lately ascertained by Ritter, Wollaston, and Davy. Scheele threw the prismatic spectrum upon a sheet of paper, moistened with a solution of nitrate of silver, a salt quickly decomposed by the agency of light. In the blue and violet rays the silver was soon reduced, producing a blackness upon the paper, but in the red ray scarcely any similar effect was observed. Wollaston and Ritter discovered that these chemical changes were most rapidly effected in the space which bounds the violet ray, and which is out of the visible spectrum.
It has thus been ascertained, that the solar beams are refrangible into three distinct kinds of rays,—the calorific, or heating rays; the colorific rays which produce colour; the decomposing rays, or those which have a tendency to interfere with the chemical constitution of bodies.
In the prismatic spectrum these three sets of rays are imperfectly separated, and arranged according to their respective refrangibilities. The heating rays are the least refrangible, the colorific rays are pos- sessed of more refrangibility, and the chemical, or, as some have called them, the deoxidizing rays, are the most refrangible.
Sir H. Davy has observed, that certain metallic oxides, when exposed to the violet extremity of the prismatic spectrum, undergo a change similar to that which would have been produced by exposure to a current of hydrogen; and that, when exposed to the red rays, they acquire a tendency to absorb oxygen. (Elements of Chemical Philosophy.) In such general facts, he traces an analogy between the effects of the solar beam, and the agencies of electricity. In the Voltaic circuit, the maximum of heat is at the positive pole, where the power of combining with oxygen is also given to bodies; the agency of rendering bodies inflammable is exerted at the opposite surface, and similar chemical effects are produced by negative electricity, and by the most refrangible rays, and by positive electricity, and the rays which are least refrangible.
PART III.
Having thus rapidly explained the laws of Attraction, Heat, and Electricity, and the phenomena exhibited by Radiant Matter, we proceed to the Elementary or Undecomposed Bodies and their mutual combinations. These bodies are between fifty and sixty in number; four are gaseous, and the remainder solids: there are no simple liquids. They may be arranged under three heads:
1. Acidifying Supporters of Combustion. 2. Acidifiable Combustibles. 3. Metals.
The first division includes three substances.
1. Oxygen. 2. Chlorine. 3. Iodine.
1. Oxygen. (From οξύς γεννάω, producer of acids.)
This elementary gaseous body may be obtained by heating to redness, in a glass retort, the salt called Oxymuriate of Potash, 100 grains of which yield about 100 cubical inches; it may be collected over water in the hydro-pneumatic apparatus. (See Chemistry, Encycl.) It is also given off from black oxide of manganese, red oxide of lead, or nitre when exposed to a red heat. It was discovered by Dr Priestley in the year 1774. (Priestley on Air, Vol. II. 154.)
Oxygen gas is insipid, colourless, and inodorous; its specific gravity is 15, hydrogen being assumed = 1. 100 cubical inches at mean temperature and pressure weigh 33.75 grains. It is a powerful supporter of respiration and combustion. A small animal confined in oxygen gas, lives thrice as long as when confined in the same bulk of common air. A lighted taper, or a burning piece of sulphur, or phosphorus introduced into this gas, is very rapidly consumed, with intense ignition.
The phenomena of combustion were referred by Stahl and his associates, to a peculiar principle which they called phlogiston: it was supposed to exist in all combustibles, and combustion was said to depend upon its separation; but this explanation was absurdly at variance with the well known fact, that bodies during combustion increase in weight.
After the discovery of oxygen gas, it was adopted by Lavoisier as the universal supporter of combustion. The basis of the gas was supposed to unite to the combustible, and the heat and light which it before contained in the gaseous state, were said to be evolved in the form of flame. But in this case, several requisites are not fulfilled; the light depends upon the combustible, and not upon the quantity of oxygen consumed; and there are very numerous instances of combustion in which oxygen, instead of being solidified, becomes gaseous during the operation; and, lastly, in others, no oxygen whatever is present. Combustion, therefore, cannot be regarded as dependent upon any peculiar principle or form of matter, but must be considered as a general result of intense chemical action. It may be connected with the electrical energies of bodies; for all bodies which powerfully act upon each other, are in the opposite electrical states of positive and negative; and the evolution of heat and light may depend upon the annihilation of these opposite states, which happens whenever they combine.
2. Chlorine. (From χλωρός, greenish yellow.)
To obtain this gas, a mixture of black oxide of manganese and muriatic acid may be heated over a lamp in a glass retort. It is soon copiously evolved, and may be conveniently collected over warm water; as it is absorbed by cold water, it cannot be long retained over that fluid.
It may also be procured in the same way from a mixture of 8 parts of common salt, 3 of black oxide of manganese, 4 of water, and 5 of sulphuric acid.
Chlorine was discovered by Scheele in 1774; it was called by him dephlogisticated muriatic acid. The term oxymuriatic acid was afterwards applied to it by the French chemists.
Chlorine is a permanently elastic gaseous fluid; it has a pungent and disagreeable smell, and is highly injurious when respired, even largely diluted with atmospheric air. Its colour is greenish yellow.
The specific gravity of chlorine, composed with hydrogen, is as 33.5 to 1; 101 cubic inches weigh 75,375 grams. At the temperature of 60°, water dissolves two volumes of chloring. The solution is of a pale yellow colour, has an astringent nauseous taste, and destroys vegetable colours, though the gas itself, when perfectly free from moisture, has scarcely any action upon them. When a burning taper is immersed in a jar of chlorine, the brilliancy of the flame is much impaired, it becomes red, throws off much charcoal, and is soon extinguished. Many bodies, such as phosphorus and several of the metals, are spontaneously ignited by chlorine, and burn in it with much brilliancy. In these cases, binary compounds result, some of which, like those of oxygen, are possessed of acid properties. Others are not acid, and such compounds with oxygen, being called oxides, those which chlorine forms may be termed chlorides.*
Chlorine was once regarded as composed of oxygen and muriatic acid, a fallacy arising from the presence of water, and which will be rendered more intelligible under the head Muriatic Acid. (See Davy's Paper, Phil. Trans. 1811.)
Chlorine and oxygen unite in two proportions, forming an oxide and an acid.
Oxide of Chlorine or Euchlorine, so called by its discoverer, Sir H. Davy (Phil. Trans. 1815), from its very deep colour, may be obtained as follows. Upon 10 or 12 grains of the salt called oxymuriate of potash, drop a small quantity of sulphuric acid, and stir the mixture with a platinum knife, having so adjusted the relative quantities of salt and acid, that they may form together a yellow powder. Put this into a very small retort or bent tube, and by a water bath, apply a temperature of 150°. Euchlorine will pass off, and may be collected over quicksilver in small jars, or tubes. The smell of this gas somewhat resembles that of chlorine, but is much less irritating and disagreeable. Its taste is astringent, and not at all acid. When gently heated, it is decomposed with explosion and expansion,—two volumes are enlarged into three, of which two consist of oxygen, and one of chlorine; it is therefore composed of 33.5 parts by weight of chlorine combined with 30 of oxygen.
Chloric acid. In the compound which has been thus called by its discoverer M. Gay-Lussac (Annales de Chimie, tom. 91, p. 108), the relative proportions of chlorine to oxygen are to each other as 33.5 to 37.5; but it is a compound which cannot exist, independent of water or some base, and, therefore, may be compared to the sulphuric acid. It may be prepared by passing a current of chlorine, through a mixture of oxide of silver † and water. Chloride of silver is produced, which is insoluble, and may be separated by filtration. The excess of chlorine which the filtered liquor contains is separable by heat, and the chloric acid dissolved in water remains. It is a sour colourless liquid, producing peculiar compounds afterwards to be described. It forms no precipitate in any metallic solution. Its compounds may be called chlorates. The most remarkable of them have been long known under the name of Oxymuriates.
3. Iodine. (From ἰώδης, violaceus.)
Iodine is procured by the following process: Lixivate powdered kelp with cold water. Evaporate the lixivium till a pellicle forms, and set aside to crystallize. Evaporate the mother liquor nearly to dryness, and pour upon the mass half its weight of sulphuric acid. Apply a gentle heat to this mixture in a glass alembic; fumes of a violet colour arise and condense in the form of opaque crystals, having a metallic lustre.
This body was discovered in 1812 by M. Courtois of Paris. Vauquelin (Annales de Chimie, t. 90), Gay-Lussac (ib. 91), and Davy (Phil. Trans. 1814), have successfully investigated its properties.
Iodine has a bluish black colour; its lustre is metallic. It is soft and friable. Its specific gravity = 4.946. It produces a yellow stain upon the skin. Its smell resembles that of diluted chlorine; its taste acid. It is extremely volatile, and, at a temperature between 60° and 80°, produces a violet vapour. At 120° or 130° it rises more rapidly. At 220° it fuses, and produces copious violet-coloured fumes, which condense in brilliant plates, and acute octoedrons. Like chlorine and oxygen, it is electro-negative; and therefore attracted by the positive surface of the Voltaic pile.
Oxiodic acid (Davy, Phil. Trans. 1815). This compound of oxygen and iodine cannot be obtained directly, for those bodies exert no mutual action. It is procured by acting upon euchlorine by iodine. A liquid is formed, which consists of chloriodic and oxiodic acids. The former is separable by a gentle heat, the latter remains as a white, semitransparent, sour, and inodorous body, very soluble in water. It consists of 117 iodine, 37.5 oxygen.
Chloriodic acid is easily obtained by the direct action of chlorine upon iodine. They unite and form crystals of a deep orange colour, deliquescent, and easily fusible and soluble. The solution is sour. This compound contains 117 iodine, 33.5 chlorine.
The second division of undecomposed substances includes those which are acidifiable and combustible. These are,
1. Hydrogen. 2. Nitrogen. 3. Sulphur. 4. Phosphorus. 5. Carbon. 6. Boron.
1. Hydrogen. (From ὑδρος, &c. the base of water.)
Hydrogen was first duly examined by Mr Caven-dish (Phil. Trans. Vol. 56). It is obtained by acting upon dilute sulphuric acid by zinc filings, and by other methods presently to be noticed.
It is an aeriform fluid, not absorbable by water. It has no taste, a slightly disagreeable smell, and may be respired for a short time, though it is instantly fatal to small animals. It is the lightest body known; and we therefore conveniently assume it as unity in speaking of the specific gravity of gases, as well as in referring to the proportions in which bodies combine. 100 cubic inches weigh at mean temperature and pressure 2.25 grains. It is inflammable.
* Sir H. Davy designates these compounds by the terminations ane and ana. † Prepared by precipitating the solution of nitrate of silver with lime-water. ble, and extinguishes flame. When pure, it burns quietly with a lambent blue flame at the surface in contact with air, but if mixed with thrice its volume of air, it burns rapidly, and with detonation.
**Hydrogen and Oxygen.**—When two volumes of hydrogen gas are mixed with one volume of oxygen gas, and the mixture inflamed in a proper apparatus by the electric spark, the gases totally disappear, and the interior of the vessel is covered with drops of pure water, equal in weight to that of the gases consumed.
If pure water be exposed to the action of Voltaic electricity, it is resolved into two volumes of hydrogen, disengaged at the negative pole; and one volume of oxygen, disengaged at the positive pole; so that water is thus proved by synthesis, and by analysis, to consist of two volumes of hydrogen, combined with one volume of oxygen. The specific gravity of hydrogen compared with oxygen, is as 1 to 15; therefore the component parts of water by weight are,
\[ \begin{align*} \text{hydrogen} & : \text{oxygen} = 1 : 7.5 \\ \text{Representative number of water} & = 8.5 \end{align*} \]
or thus,
\[ \begin{array}{c|c|c} \text{H} & \text{O} & \text{water} \\ \hline 1 & 7.5 & 8.5 \end{array} \]
The mechanical and other properties of water are discussed at length in the body of the work. Its composition was discovered by Mr Cavendish in 1781.
**Hydrogen and Chlorine.**—When equal volumes of these gases are mixed, and exposed to light, they combine, and produce a sour compound, commonly called muriatic acid gas; or, in conformity to more modern nomenclature, hydrochloric acid gas. The best mode of showing the composition of muriatic acid, is to introduce into a small but strong glass vessel a mixture of the two gases, and to inflame them by the electric spark; no change of volume ensues, and muriatic gas results. This compound may be decomposed by the action of several of the metals. Potassium, for instance, absorbs the chlorine, and the hydrogen is evolved; and muriatic acid gas thus affords half its volume of hydrogen. As the specific gravity of hydrogen to chlorine is as 1 to 33.5, muriatic acid will consist of 1 hydrogen + 33.5 chlorine, and its representative number will be 34.5.
\[ \begin{array}{c|c|c} \text{H} & \text{C} & \text{Muriatic Acid} \\ \hline 1 & 33.5 & 34.5 \end{array} \]
Muriatic acid may also be readily procured by acting upon common salt by sulphuric acid, the evolved gas must be received over mercury. It was first obtained pure by Dr Priestley; but its composition was discovered by Scheele, and has since been most ably investigated by Davy. Muriatic acid gas extinguishes flame; it is sour and acrid. Its specific gravity, compared with hydrogen, is \(= 17.25\) to 1. 100 cubic inches \(= 39.5\) grains. It is greedily absorbed by water, which takes up 480 times its bulk, and has its specific gravity increased from 1 to 1.210. Thus dissolved in water, it forms the liquid muriatic acid or spirit of salt, and may easily be procured by distilling a mixture of dilute sulphuric acid and common salt.
**Hydrogen and Iodine** exert a slow action under ordinary circumstances; but when iodine is presented to nascent hydrogen, they readily unite, and produce a gaseous acid, the hydriodic acid. It is prepared by the action of moist iodine upon phosphorus, and must be received over mercury. It is colourless, very sour, and smells like muriatic acid. Its specific gravity to hydrogen is as 60.7 to 1. It is instantly decomposed by chlorine, which produces muriatic acid, and the blue vapour of iodine is rendered evident.
It consists of
\[ \begin{array}{c|c|c} \text{hydrogen} & \text{iodine} \\ \hline 1 & 117 \end{array} \]
Hydriodic acid \(= 118\)
2. **Nitrogen.** (i.e. produce of nitric acid.)
This was first recognised as a distinct aeriform fluid by Dr Rutherford in 1772. (Thesis, De aere Me- phitico.) It may be obtained by heating phosphorus in a confined portion of dry atmospheric air, which is a mixture of nitrogen and oxygen; the phosphorus absorbs the latter, and the former gas remains. After repeated washing with lime-water, it may be considered as pure.
100 cubic inches weigh 29.25 grains; so that its specific gravity, compared with hydrogen, is as 13 to 1. It is tasteless, inodorous, and insoluble in water. It does not support combustion, and is fatal to animals; hence was called azote. It is not inflammable; but when its compounds are submitted to Voltaic decomposition, it is attracted by the negative pole.
**Nitrogen and Oxygen.**—These bodies unite in four proportions, and form the compounds called,
1. Nitrous oxide. 2. Nitric oxide. 3. Nitrous acid. 4. Nitric acid.
Nitrous oxide may be obtained by distilling nitrate of ammonia at a temperature of about 420°. The gas which passes off may be collected over water, and is nitrous oxide. 100 cubic inches weigh 46.125 grains; its specific gravity, therefore, to hydrogen is as 20.5 to 1. The taste of this gas is sweet, and its smell peculiar, but agreeable. Its singular effects resembling intoxication when respired, were first ascertained by Sir H. Davy. It supports combus- Nitric Oxide is usually obtained by presenting certain substances to nitric acid, which abstract a portion of its oxygen, leaving the remaining element in such proportion as to constitute the gas in question; for this purpose, some copper filings may be put into a gas bottle with nitric acid diluted with thrice its bulk of water; an action ensues, red fumes are produced, and there is a copious evolution of the gas, which may be collected and preserved over water. This gas is presently recognised by the red fumes which it produces when brought into the contact of air.
It extinguishes most burning bodies, but phosphorus readily burns in it. Its specific gravity to hydrogen is as 14 to 1. 100 cubic inches weigh = 31.5 grains.
It does not detonate when mixed with oxygen, and subjected to the electric spark; but it may be decomposed by the action of some of the metals at high temperatures, which absorb its oxygen. One volume of nitric oxide is thus resolved into equal volumes of oxygen and nitrogen. If, therefore, we call nitrous oxide a compound of 1 proportion of nitrogen + 1 oxygen, then nitric oxide may be considered as consisting of 1 nitrogen + 2 oxygen, or by weight, 13 nitrogen + 15 oxygen, and its symbol will stand thus:
| Nitrogen | Oxygen | |----------|--------| | 13 | 7.5 |
Nitric Acid Gas.—When nitric oxide is presented to oxygen, the two gases combine, and a new gaseous compound of a deep orange colour results. This compound is not easily examined, because it is absorbed both by quicksilver and water, so that we are obliged to resort to exhausted glass vessels for its production. When we thus mix two volumes of nitric oxide with one volume of oxygen, the gases become condensed to about half their original volumes, and form nitrous acid gas. This gas supports the combustion of the taper, of phosphorus, and of charcoal, but extinguishes sulphur. It is readily absorbed by water, forming a green sour liquid. Its specific gravity to hydrogen is as 28.6 to 1, and 100 cubic inches = 64.48 grains.
It is obvious that this nitrous acid gas must consist of 13 nitrogen + 30 oxygen, and, therefore, its number is 43, for nitric oxide is composed of equal volumes of nitrogen and oxygen, and one additional volume of oxygen, or two proportions by weight are added to form nitrous acid.
Nitric Acid.—The fourth compound of nitrogen with oxygen is the nitric acid; the nature of which was first demonstrated by Mr Cavendish in 1785. (Phil. Trans.) It is usually obtained from nitre, three parts of which are distilled with two of sulphuric acid.
The nitric acid is a colourless liquid, extremely sour and corrosive. Its specific gravity is 1.42; it always contains water, which modifies its specific gravity. At 25° it boils and distils over without change. At 40° it congeals. It absorbs water from the air, and its bulk is thus increased, while its specific gravity is diminished. It is usually coloured by nitrous acid gas.
Nitric acid in its dry state, that is, as it exists combined with metallic oxides, may be regarded as composed of one proportion of nitrogen = 13, and 5 of oxygen = 37.5, and this will be the symbol representing its composition.
Consequently, the representative number of dry nitric acid is 50.5. But in its liquid state it always contains water, and when, in this state, its specific gravity is 1.5, it may be regarded as a compound of one proportion of dry acid and two of water, and this may be numerically expressed thus:
\[ \text{Acid. Water} \] \[ 50.5 + 17 = 67.5 \text{ liquid acid spe. grav. } 1.5. \]
Nitromuriatic Acid.—This term has been applied to the Aqua Regia of the alchemists. When nitric and muriatic acids are mixed, they become yellow, and acquire the power of readily dissolving gold, which neither of the acids possessed separately. This mixture evolves chlorine, a partial decomposition of both acids having taken place, and water, chlorine, and nitrous acid. gas, are thus produced; that is, the hydrogen of the muriatic acid abstracts oxygen from the nitric to form water. The result must be chlorine and nitrous acid. (Davy, Journal of Sciences and the Arts, Vol. I. p. 67.)
Nitrogen and Chlorine.—These gases do not unite directly, but the compound may be obtained by exposing a solution of nitrate or muriate of ammonia to the action of chlorine, at a temperature of 60° or 70°. The gas is absorbed, and an oil-like fluid, heavier than water, is produced. It was discovered by M. Dulong. (Annales de Chimie, Vol. LXXXVI.) Its specific gravity is 1.6; it is not congealed by cold. This substance is dangerously explosive, and is decomposed with violent detonation by many combustibles, especially phosphorus, and fixed oils. Alcohol quietly changes it into a white substance. Mercury absorbs the chlorine, and evolves nitrogen. It yields, by decomposition, 1 volume of nitrogen and 4 of chlorine; and as the specific gravity of nitrogen to chlorine is as 13 to 33.5, so it may be said to consist of 1 proportion of nitrogen + 4 proportions of chlorine, or \( \frac{13}{13} + \frac{13}{4} \) by weight, and its number will be 147.
Nitrogen and Iodine.—A compound of these bodies may be procured by pouring a solution of ammonia upon a very small quantity of iodine. Hydroic acid is one product, and the other a brown powder, which detonates upon the slightest touch, and is resolved into nitrogen and iodine.
Nitrogen and Hydrogen—Ammonia or Volatile Alcali.—This gaseous compound may be obtained by heating a mixture of quicklime and muriate of ammonia. It must be collected over mercury. It is a permanently elastic gas at common temperatures, extremely pungent and acrid, but when diluted by mixture with common air, agreeably stimulant. It converts most vegetable blues to green, and the yellows to red, properties which belong to the bodies called alcalies. Ammonia, therefore, has been termed volatile alcali.
Its specific gravity to hydrogen is as 8 to 1—100 cubical inches weighing 18 grains. It extinguishes flame, but forms an inflammable mixture with common air and with oxygen.
Water at the temperature of 50° takes up 670 times its volume of ammonia; its bulk is increased, and specific gravity diminished; that of a saturated solution is 0.875, water being 1.000. Ammonia may be decomposed by detonation with oxygen; also by passing it through a red hot iron tube. It yields one volume of nitrogen and three of hydrogen, and therefore consists by weight of 13 nitrogen 3 + hydrogen, and its representative number is 16.
Ammonia and Chlorine.—When these gases are mixed, a partial decomposition of the former ensues. On mixing 15 parts of chlorine and 40 of ammonia, heat and light are evolved; 5 parts of nitrogen are liberated, and muriate of ammonia is formed.
Ammonia and Muriatic Acid—Muriate of Ammonia—Sal Ammoniac.—This salt may be produced directly by mixing equal volumes of ammonia and muriatic acid, when an entire condensation ensues.
| Nitrogen | Chlorine | |----------|----------| | 13 | 33.5 |
The specific gravity of ammonia to muriatic acid is as 16. to 34.5, therefore, muriate of ammonia consists of 34.5 muriatic acid + 16 ammonia.
Ammonia and Nitric Acid—Nitrate of Ammonia.—This salt may be procured by the direct union of ammonia with nitric acid—or more easily by saturating dilute nitric acid with carbonate of ammonia. It has been mentioned as the source of nitrous oxide, and when heated is entirely resolved into that gas and water. It consists of one proportion of nitric acid = 50.5 + one proportion of ammonia = 16, and therefore the representative number of the nitrate of ammonia is 66.5. Or it may be considered as containing 2 proportions of nitrogen, 3 of hydrogen, and 5 of oxygen, as the following symbols show:
Nitric Acid.
| Nitrogen | Oxygen | |----------|--------| | 13 | 7.5 | | | 7.5 | | | 7.5 | | | 7.5 | | | 7.5 |
\( 37.5 + 50.5 \)
Acid. Ammo. Nitrat. of Ammonia
\( 50.5 + 16 = 66.5 \)
Ammonia.
| Nitrogen | Hydrogen | |----------|----------| | 13 | 1 | | | 1 | | | 1 |
\( 3 = 16 \)
Nitrous oxide consists of 1 proportion of nitrogen = 13 + 1 of oxygen = 7.5; hence the two proportions of nitrogen in the salt (1 in the acid and 1 in the ammonia) will require two of oxygen to produce nitrous oxide, and the remaining 3 of oxygen will Chemistry. unite to the 3 of hydrogen, and form water. And accordingly nitrous oxide and water are the only possible results; so that the elements, after the decomposition of the salt, are arranged thus:
\[ \begin{align*} \text{Nitrogen} & \quad \text{Oxygen} \\ 13 & \quad 7.5 \\ \end{align*} \]
\[ \begin{align*} \text{Nitrogen} & \quad \text{Oxygen} \\ 13 & \quad 7.5 \\ \end{align*} \]
= Nitrous oxide.
\[ \begin{align*} \text{Hydrogen} & \quad \text{Oxygen} \\ 1 & \quad 7.5 \\ \end{align*} \]
\[ \begin{align*} \text{Hydrogen} & \quad \text{Oxygen} \\ 1 & \quad 7.5 \\ \end{align*} \]
= Water.
Atmospheric Air may be considered as a mixture of 21 per cent. of oxygen with 79 of nitrogen; 100 cubical inches at mean pressure and temperature weigh 30,195 grains, and its specific gravity compared with hydrogen is as 13.42 to 1.
3. Sulphur.
A substance of a pale yellow colour, insipid and inodorous, but exhaling a peculiar smell when heated. Its specific gravity is 1,990. It is principally a mineral product, and occurs crystallized, its primitive form being a very acute octoëdron, with an oblique base. When sulphur is heated to about 10° it volatilizes, and its peculiar odour is strong and disagreeable: at 225° it liquefies; between 350° and 400° it becomes viscid, and of a deep brown colour; and at about 600° it quickly sublimes. When slowly cooled after fusion, it forms a fibrous crystalline mass.
Sulphur forms compounds with oxygen, chlorine, iodine, and hydrogen.
Sulphur and Oxygen.—To oxygen it unites in two proportions, giving rise to the compounds, sulphurous and sulphuric acid. Sulphurous acid, or, as it should rather be called, sulphurous oxide, is a gaseous body, which may be obtained by several processes. It may be procured directly by burning sulphur in oxygen gas, or indirectly by heating mercury in sulphuric acid. It must be collected and preserved over mercury, for water takes up rather more than 30 times its bulk of this gas, forming the liquid sulphurous acid, which, when recently prepared, has a sulphureous astringent taste, and destroys many vegetable colours; but by keeping it acquires a sour flavour, and reddens the generality of vegetable blues. If sulphur be burned in oxygen, sulphurous acid is produced, without any change in the volume of the gas, so that its composition is easily learned by the increase of weight; and as 100 cubic inches of oxygen (weighing 33.75 grains) dissolve 33.75 grains of sulphur, it is obvious that the sulphurous acid is composed of equal weights of sulphur and oxygen; and if we regard it as consisting of two proportions of oxygen and one of sulphur, the latter element will be represented by the number 15; and the sulphurous acid, consisting of 1 proportion of sulphur = 15, and 2 proportions of oxygen = 15, will be represented by 30, which is also its relative specific gravity to hydrogen, considering the latter as = 1; 100 cubical inches of sulphurous acid gas weigh 67.5 grains. This gas has a suffocating nauseous odour, an astringent taste; it extinguishes flame, and kills animals. When mixed in equal volume with ammonia, a yellowish salt is produced, which is a sulphite of ammonia, and which consists of 60 sulphurous acid + 16 ammonia.
Sulphuric Acid.—This body was formerly obtained by the distillation of green vitriol, and called oil of vitriol. It is now procured in this country by burning a mixture of 8 parts of sulphur and 1 of nitre in close chambers containing water, by which the fumes produced are absorbed, and by evaporation the acid is procured in a more concentrated state.
Sulphuric acid, as usually met with, is a limpid colourless fluid, having a specific gravity of 1.85,—it boils at 620°, and freezes at 15°. It is very acid and caustic, and when diluted with water, produces a very sour liquid. It rapidly absorbs water from the atmosphere, and upon sudden mixture with water produces much heat.
In sulphuric acid 1 proportion of sulphur = 15, is combined with 3 proportions of oxygen = 22.5, and, consequently, dry sulphuric acid is correctly represented by 15 + 22.5 = 37.5, but it only exists in this state (like the nitric and chloric acids) when united with bases, and in its ordinary state contains water, and should, therefore, be called Hydro-sulphuric Acid. It has been found by experiment, that 100 parts of sulphuric acid, specific gravity 1.9, contain 18.2 of water, consequently, it may be looked upon as composed of 1 sulphur + 3 oxygen + 1 water:
or of
\[ \begin{align*} 15 \text{ sulphur} \\ 22.5 \text{ oxygen} \\ 8.5 \text{ water} \\ \end{align*} \]
46 = number for liquid sulphuric acid.
The formation of sulphuric acid by the combustion of sulphur and nitre is as follows:
The sulphur, by burning in contact with atmospheric air, forms sulphurous acid. The nitre gives rise to the production of nitric oxide, which, with the oxygen of the air, produces nitrous acid gas. When these gases (i.e., sulphurous and nitrous acids) are perfectly dry, they do not act upon each other, but moisture being present in small quantity, they form a white solid, which is instantly decom- posed when put into water; the nitrous acid reverts to the state of nitric oxide, having transferred one additional proportion of oxygen to the sulphurous acid, and, with water, producing the sulphuric acid; while the nitric oxide, by the action of the air, again affords nitrous acid, which plays the same part as before.
Sulphurous acid consists of
\[ \begin{align*} \text{Sulphur} & : \quad 15 \\ \text{Nitrogen} & : \quad 13 \\ \text{Oxygen} & : \quad 7.5 \\ \end{align*} \]
15; and nitrous acid contains
\[ \begin{align*} \text{Nitrogen} & : \quad 13 \\ \text{Oxygen} & : \quad 7.5 \\ \end{align*} \]
30; hence every two portions of sulphurous acid require one of nitrous acid, which transfers two of oxygen, and passes back into the state of nitrous gas, sulphuric acid being, at the same time, produced. The sulphurous acid and nitrous acid, therefore, before decomposition, may be thus represented:
\[ \begin{align*} \text{Sulphur} & : \quad 15 \\ \text{Nitrogen} & : \quad 13 \\ \text{Oxygen} & : \quad 7.5 \\ \end{align*} \]
And after decomposition as follows:
\[ \begin{align*} \text{Sulphur} & : \quad 15 \\ \text{Nitrogen} & : \quad 13 \\ \text{Oxygen} & : \quad 7.5 \\ \end{align*} \]
The decomposition of sulphuric acid may be effected by passing it through a red hot platinum tube, when it is resolved into sulphurous acid, oxygen, and water. Its uses are numerous and important.
**Sulphuric Acid and Ammonia—Sulphate of Ammonia**—may be obtained by passing ammonia into sulphuric acid, but is usually prepared by saturating dilute sulphuric acid with carbonate of ammonia. By crystallization it affords six sided prisms. This salt is important as a source of the muriate of ammonia. It dissolves in twice its weight of water at 60°, and consists of 1 proportion of sulphuric acid \(= 37.5 + 1\) proportion of ammonia \(= 16\). Its number, therefore, is 55.5. When heated, ammonia is given off, and a supersulphate remains, consisting of 2 proportions of acid \(+ 1\) of alkali.
**Sulphur and Chlorine—Chloride of Sulphur.**—When sulphur is heated in chlorine, it absorbs rather more than twice its weight of that gas. 10 grains of sulphur absorb 30 cubic inches of chlorine, and produce a greenish-yellow liquid, consisting of 15 sulphur \(+ 33.5\) chlorine, and represented, therefore, by the number 48.5. It exhales suffocating and irritating fumes when exposed to the air. Its specific gravity \(= 1.6\). It does not affect dry vegetable blues; but when water is present, instantly reddens them. Sulphur is deposited, and sulphurous, sulphuric, and muriatic acids are formed in consequence of a decomposition of the water.
**Sulphur and Iodine** readily unite, and form a black crystallizable compound.
**Sulphur and Hydrogen—Sulphuretted Hydrogen Gas.**—This gaseous compound of sulphur and hydrogen was discovered by Scheele in 1777. It may be obtained by presenting sulphur to nascent hydrogen, which is the case when sulphuret of iron is acted upon by dilute sulphuric acid. This gas may be collected over water, though, by agitation, that fluid absorbs thrice its bulk. It has a fetid odour. Its specific gravity to hydrogen is as 16 to 1. 100 cubic inches \(= 36\) grains. It extinguishes flame; and, when respired, proves fatal. It is very deleterious, even though largely diluted with atmospheric air. When one volume of sulphuretted hydrogen, and 1/3 of oxygen, are inflamed in a detonating tube, 1 volume of sulphurous acid is produced, and water is formed. Thus the sulphur is transferred to one volume of the oxygen, and the hydrogen to the half volume. Sulphuretted hydrogen, therefore, consists of 15 sulphur \(+ 1\) hydrogen, and its number is 16.
Chlorine and iodine instantly decompose sulphuretted hydrogen; sulphur is deposited, and hydrochloric and hydriodic acids are formed.
Sulphuretted hydrogen and ammonia readily unite in equal volumes, and produce **hydrosulphuret of ammonia**. At first white fumes appear, which become yellow. A yellow crystallized compound results, consisting of 16 sulphuretted hydrogen, 8 ammonia. It is of much use as a test for the metals, and may be procured by distilling, at nearly a red heat, a mixture of 6 parts of slacked lime, 2 of muriate of ammonia, and 1 of sulphur.
There is another compound of hydrogen and sulphur, which has been called supersulphuretted hydrogen. It is a liquid, formed by adding muriatic acid to a solution of sulphuret of potash, and appears to consist of two proportions of sulphur = 30 + one of hydrogen = 1.
Sulphur and nitrogen do not combine. Sulphur always, in its ordinary state, contains hydrogen, which it gives off during the action of various bodies, for which it has a powerful attraction.
4. Phosphorus
Is obtained by distilling phosphoric acid with charcoal at a red heat. When pure, it is nearly colourless, semitransparent, and flexible. Its specific gravity = 1.770. It melts, when air is excluded, at 105°. If suddenly cooled after having been heated to 140°, it becomes black; but if slowly cooled, remains colourless. At 500°, it boils, and rapidly evaporates. When exposed to air, it exhales luminous fumes, having a peculiar alliaceous odour; it is tasteless. At a temperature of about 100°, it takes fire, and burns with intense brilliancy, throwing off copious white fumes. If, instead of burning phosphorus with free access of air, it be heated in a confined portion of very rare air, it enters into less perfect combustion, and three compounds of phosphorus with oxygen are the result, each characterized by distinct properties. The first is a red solid, less fusible than phosphorus; the second is a white substance, more volatile than phosphorus; the third a white and fixed body.
The red solid consists of a mixture of phosphorus and oxide of phosphorus. Oxide of phosphorus is the white substance with which phosphorus becomes encrusted when kept for some time in water. It is very inflammable, and less fusible and volatile than phosphorus.
Phosphorous acid is best procured by mixing chloride of phosphorus with water, filtering and evaporating the solution, when a white crystallized solid is obtained, which is a compound of the phosphorous acid with water. (See Chloride of Phosphorus.)
The phosphoric acid may be produced by burning phosphorus in excess of oxygen. There is intense heat and light produced, and white deliquescent flocculi line the interior of the receiver. Phosphoric acid may also be obtained by acting upon phosphorus by nitric acid.
The composition of phosphoric acid is learned by ascertaining the bulk of oxygen absorbed during the perfect combustion of a given weight of phosphorus, which is = 4.4 cubic inches for each grain; so that 100 grains of phosphorus would require, for conversion into phosphoric acid, 440 cubic inches of oxygen = 148.5 grains. Hence phosphoric acid, considered as a compound of one proportion of phosphorus, and two proportions of oxygen, will consist of 10 phosphorus + 15 oxygen.
Phosphoric acid is a deliquescent substance; when fused it has been called Glacial Phosphoric Acid. It is inodorous, very sour, fixed in the fire, and unchanged by heat. As commonly prepared, it is an unctuous fluid. Specific gravity = 2.
Phosphite of Ammonia may be obtained in delicate annular crystals, decomposable by heat.
Phosphate of Ammonia is a common ingredient in the urine of carnivorous animals. It may be obtained pure by saturating phosphoric acid with ammonia, and forms crystals in four-sided prisms.
Phosphorus and Chlorine.—These elements unite in two proportions, forming two definite compounds,—the chloride and bichloride of phosphorus. When phosphorus is submitted to the action of chlorine, it burns with a pale yellow flame, and produces a white volatile compound, which attaches itself to the interior of the vessel. This substance was long mistaken for phosphoric acid, but its volatility is alone sufficient distinction; it rises in vapour at 200°. It is fusible and crystallizable; and when brought into the contact of water, a mutual decomposition is effected, and phosphoric and muriatic acids result. When passed through a red-hot porcelain tube with oxygen, phosphoric acid is produced, and chlorine evolved.
With ammonia it forms a singular compound, which, though consisting of three volatile bodies, remains unchanged at a white heat,—it is insoluble in water.
When phosphorus is burned in chlorine, one grain absorbs nine cubic inches; so that the compound formed must be regarded as the bichloride, and consists of 10 of phosphorus + 67 of chlorine, and its number is 77.
The Chloride of Phosphorus, consisting of 10 phosphorus + 33.5 chlorine, is procured by distilling a mixture of phosphorus and corrosive sublimate, which is a bichloride of mercury. In this experiment calomel, or chloride of mercury, is formed, and the phosphorus combines with one proportion of chlorine.
The chloride of phosphorus, when first obtained, is a liquid of a reddish colour; it soon deposits a portion of phosphorus, however, and becomes limpid and colourless. Its specific gravity = 1.45. Exposed to the air it exhales acid fumes; it does not change the colour of dry vegetable blues. Chlorine converts it into bichloride. Ammonia separates phosphorus, and produces the singular triple compound before adverted to.
Chloride of phosphorus acts upon water with great energy, and produces muriatic and phosphorous acids, while the bichloride produces muriatic and phosphoric acids: for as in the bichloride there are two proportions of chlorine, so, in acting upon water, two of oxygen must be evolved, which, uniting to one of phosphorus, generate phosphoric acid. The chloride of phosphorus, on the contrary, containing only one proportion of chlorine, produces muriatic acid and phosphorous acid, when it decomposes water.
Before decomposition.
| Chlorine | Phosphorus | |----------|------------| | 1 Chlorine = 33.5 | 1 Phospho. = 10 | | 1 Hydrog. = 1 | 1 Oxygen = 7.5 |
Water. After decomposition.
| Muriatic Acid | Phosphoric Acid | |---------------|----------------| | Chlorine = 33.5 | Phosphorus = 10 | | Hydrogen = 1 | Oxygen = 7.5 |
But the phosphorous acid thus produced always contains water, which it throws off when heated in ammonia, forming, with that alkali, a dry phosphite. This experiment shows that the Hydrophosphorous acid consists of 2 proportions of phosphorous acid \(= 35 + 1\) water \(= 8.5\).
**Phosphorus and Iodine.**—When these substances are brought together in an exhausted vessel, they act violently, and form a reddish compound; it decomposes water with great energy, and produces phosphorous and hydroiodic acids.
**Phosphorus and Hydrogen.**—When phosphorus is presented to nascent hydrogen, two gaseous compounds result. The one inflames spontaneously upon the contact of the atmosphere. This may be procured by heating phosphorus in a solution of caustic potash, or better, by acting upon phosphuret of lime by dilute muriatic acid. The gas may be collected over water. It is colourless, has a nauseous odour like onions, a very bitter taste, and inflames when mixed with air, a property which it loses by being kept over water. For our knowledge of the properties and composition of this gas we are chiefly indebted to Dr Thomson, who has shown that the hydrogen suffers no change of bulk in uniting to the phosphorus; so that the difference of weight between this gas and pure hydrogen indicates the weight of phosphorus: 100 cubic inches of phosphuretted hydrogen \(= 24.75\) grains; hence the gas may be regarded as containing one proportion of phosphorus and one of hydrogen, or \(10 + 1 = 11\).
The next compound of phosphorus and hydrogen has been called, by Sir H. Davy, hydrophosphoric gas. It is procured by heating the solid hydrophosphorous acid. The gas must be collected over mercury. Its specific gravity to hydrogen is as 12 to 1. It is not spontaneously inflammable, but explodes when heated with oxygen. It inflames spontaneously in chlorine. It smell is less disagreeable than the former. It consists of 2 of hydrogen and 1 of phosphorus \(2 + 10 = 12\); but the two volumes of hydrogen are condensed into one. 100 cubic inches weigh 27 grains.
When hydrophosphorous acid is decomposed for the production of this gas, phosphoric acid is always generated. Hydrophosphorous acid has been stated to contain two proportions of phosphorous acid + one of water. Hence the elements
\[ \begin{align*} 20 \text{ phosphorus} & = \text{ phosphorous acid}, \\ 15 \text{ oxygen} & = \text{ water}, \end{align*} \]
or 43.5 parts of hydrophosphorous acid contain
\[ \begin{align*} 20 \text{ phosphorus} & = 22.5 \text{ oxygen}, \\ 1 \text{ hydrogen} & = 1 \text{ hydrogen}. \end{align*} \]
The three proportions of oxygen \(= 22.5\) will require one proportion and a half of phosphorus \(= 15\) to form phosphoric acid, and the remaining half proportion of phosphorus will unite to the one of hydrogen to form hydrophosphoric gas, which consist of 5 phosphorus + 1 hydrogen.
To avoid fractions the phenomena may be stated thus:
Four proportions of hydrophosphoric acid contain
\[ \begin{align*} 4 \text{ phosphorus} & = 40, \\ 4 \text{ oxygen} & = 30, \\ 2 \text{ do.} & = 15, \\ 2 \text{ hydrogen} & = 2. \end{align*} \]
The whole of the oxygen, amounting to 6 proportions (\(i.e.\) \(7.5 \times 6 = 45\)), unites to three proportions of phosphorus \((10 \times 3 = 30)\) to form phosphoric acid. The two of hydrogen \(= 2\), combine with the remaining proportion of phosphorus \(= 10\) to form hydrophosphoric gas.
**Phosphorus and Nitrogen** produce no definite compound.
**Phosphorus and Sulphur** may be readily united by fusion in an exhausted vessel. When one proportion of phosphorus is united to one of sulphur \((10 + 15)\), the compound bears a high temperature without decomposition.
### 5. Carbon.
The purest form of this element is the diamond, a colourless transparent body found in certain alluvial strata; its primitive crystalline form is the regular octoëdron. Its specific gravity \(= 3.50\).
Another form of carbon is charcoal, and of this the purest variety is lamp-black. Charcoal is possessed of some very curious properties in regard to absorbing gases, and removing the colour, smell, and taste of certain vegetable and animal bodies.
**Carbon and Oxygen.**—There are two compounds of carbon and oxygen,—the carbonic oxide and the carbonic acid.
Carbonic Oxide is usually obtained by subjecting carbonic acid to the action of substances which abstract a portion of its oxygen. Upon this principle, carbonic oxide gas is produced by heating chalk and charcoal, or chalk and iron or zinc filings. The gas should be well washed, and may be preserved over water. Its specific gravity to hydrogen is as 13.2 to 1; 100 cubical inches weighing 29.7 grains. It is fatal to animals, extinguishes flame, and burns with a pale blue lambeant light when mixed with, or exposed to, atmospheric air. When a stream of carbonic oxide is burnt under a dry bell glass of air or oxygen, no moisture whatever is deposited. When two volumes of carbonic oxide and one of oxygen are acted on by the electric spark, a detonation ensues, and two volumes of carbonic acid are produced. Whence it appears, that carbonic acid contains just twice as much oxygen as carbonic oxide. Carbonic oxide may be considered as a compound of one volume of oxygen and one volume of gaseous carbon, or of one proportion of carbon and one of oxygen, the latter being so expanded as to occupy two volumes. The representative number of charcoal, as obtained by considering this gas as a compound of one proportion of charcoal and one of oxygen, is 5.7 and 5.7 carbon + 7.5 oxygen = 13.2 carbonic oxide.
Carbonic acid may be obtained by burning carbon, either pure charcoal or the diamond, in oxygen gas; the oxygen suffers no change of bulk, so that the composition of carbonic acid is easily learned by comparing its weight with that of an equal volume of pure oxygen: 100 cubic inches of oxygen weigh 33.75 grams; 100 cubic inches of carbonic acid weigh 46.57 grams; hence 100 cubical inches of carbonic acid must consist of 33.75 grams of oxygen, + 12.82 grams of carbon, and 12.82:33.75:5.7:15. Hence one proportion of charcoal = 5.7 + 2 proportions of oxygen, = 15, will constitute carbonic acid, represented by the number 20.7.
Carbonic acid is a most abundant natural product; the best mode of procuring it for experiment consists in acting upon pounded marble (carbonate of lime) by dilute muriatic acid. It may be collected over water, but must be preserved in vessels with glass stoppers, since water, at common temperature and pressure, takes up its own volume: under a pressure of two atmospheres it dissolves twice its volume, and so on. It becomes brisk and tart; by freezing, boiling, or exposure to the vacuum of the air-pump, the gas is given off again.
Carbonic Acid and Ammonia—Carbonate of Ammonia.—These gases readily combine, and produce one of the most useful and best known of the ammoniacal compounds.
When one volume of carbonic acid and two volumes of ammonia are mixed in a glass vessel, over mercury, a complete condensation ensues, and a subcarbonate of ammonia is produced.
It consists of 16 ammonia + 20.7 carbonic acid, and is represented by 36.7:
| Carbonic Acid | Ammonia | |---------------|---------| | 20.7 | 16 |
If water be present, it so far overcomes the elasticity of the gas, as to enable the salt formed to take up another volume of carbonic acid, and thus a bicarbonate is formed.
Subcarbonate of ammonia crystallizes in octahedrons, though it is generally met with in cakes broken out of the subliming vessel, being obtained by sublimation from a mixture of muriate of ammonia and chalk. Its odour is pungent; its taste hot and saline. A pint of water at 60° dissolves rather less than 4 ounces; by exposure to air it loses ammonia, and becomes a bicarbonate.
Chlorine and carbon do not combine; but chlorine unites with carbonic oxide, and produces a triple compound, called by Dr Davy phlogene gas, as it is most easily produced by exposing a mixture of equal volumes of chlorine and carbonic oxide to the action of light. A condensation = 0.5 takes place. The compound has a peculiar pungent odour. It is soluble in water, and is resolved into carbonic and muriatic acid gases. The weight of phlogene to hydrogen is as 46.7 to 1. 100 cubical inches weigh 107,075 grains. It condenses four times its volume of ammoniacal gas, producing a peculiar compound of a white colour.
Carbon and Hydrogen.—These bodies combine in two proportions, and form gaseous compounds, consisting of 1 carbon + 1 hydrogen, and 1 carbon + 2 hydrogen.
There are several processes by which they may be obtained. The first compound is obtained by the decomposition of alcohol by sulphuric acid. It may be collected over water; its specific gravity to hydrogen is 13.4. 100 cubic inches weigh 30.15 grams.
This gas is inflammable, burning with a bright yellowish white flame. One part by volume requires for perfect combustion three of oxygen, and two of carbonic acid result. When sulphur is heated in one volume of this gas, charcoal separates, and two volumes of sulphuretted hydrogen result. As hydrogen suffers no change of volume by combining with sulphur, it follows that carburetted hydrogen contains two volumes of hydrogen condensed into one, hence the quantity of oxygen required for its consumption.
Before detonation. After detonation.
| C. Hyd. Oxygen. | Hydrogen. | Oxygen. | |-----------------|-----------|---------| | 5.7 + 1 | 7.5 | 7.5 | | 7.5 | | | | 7.5 | | |
Carbon.
| Oxygen. | |---------| | 5.7 | | 7.5 | | 7.5 |
Carbonic acid.
This gas, therefore, is constituted of 1 proportion of charcoal = 5.7 + 1 proportion of hydrogen = 1, and its number is 6.7.
When this gas is mixed with chlorine in the proportion of 1 to 2 by volume, the mixture on inflammation produces muriatic acid, and charcoal is abundantly deposited; but if the two gases be mixed in an exhausted vessel, or over water, they act slowly upon each other, and a peculiar fluid is formed, which appears like a heavy oil, hence this variety of carburetted hydrogen has been termed olefiant gas.
The other variety of carburetted hydrogen is often generated in stagnant ponds. It may be procured by passing the vapour of water over red-hot charcoal, and washing the gas thus afforded in lime-water, by which the carbonic acid is separated. 100 cubic inches of this gas weigh only 17.325 grams, so that its specific gravity to hydrogen is 7.7. It burns with a pale blue flame. It requires for perfect combustion twice its volume of oxygen; water is generated, and one volume of carbonic acid results, so that it contains only half the quantity of carbon existing in the former compound, or it may be considered as composed of carbon $5.7 + 2$ hydrogen.
| Before detonation | After detonation | |-------------------|------------------| | Carbon | | | C. Hydrogen | Oxygen | | 2.85 + 1 | 7.5 | | | | | | | | Hydrogen | Oxygen | | 1 | 7.5 | | | | | | Water |
The hydrogen in this, as in the former case, condensed to half its volume by union with carbon.
This variety of carburetted hydrogen is abundant in many coal mines, when it is often productive of terrible explosion, and known under the name of fire-damp.
There are many vegetable and animal substances, which, when submitted to destructive distillation, yield, among other products, a mixture of the two kinds of carburetted hydrogen. This is especially the case with pit-coal, the gas from which is importantly employed for the purposes of illumination.
Carbon and Nitrogen—Carburet of Nitrogen—Cyanogen.—This gaseous compound was discovered in 1815 by Gay-Lussac. It may be obtained by gently heating the Prussiate of mercury. The gas evolved must be collected over mercury. It has a penetrating and very peculiar smell; it burns with a purple flame. Its specific gravity to hydrogen is $24.4 : 100$ cubic inches weighing $54.9$ grains. Water dissolves $4.5$ volumes, and alcohol $23$ volumes of this gas. It reddens vegetable blues. It may be analyzed by detonation with oxygen. One volume detonated with two of oxygen produces two volumes of carbonic acid, and one of nitrogen. Whence it appears that cyanogen consists of two proportions of carbon $= 11.4$, and one of nitrogen $= 13$, the nitrogen having suffered no change of bulk by uniting with the carbon,—or it may be said to consist of $2$ volumes of gaseous carbon $+ 1$ volume of nitrogen, the $3$ being condensed into $1$ volume.
| Before detonation | After detonation | |-------------------|------------------| | Cyanogen | Oxygen | | C. N. | 11.4 + 13 | | | 15 | | | | | | Nitrogen | | | 13 | | | Carbonic Acid | | | Car. 114 | | | Oxy. + 30 |
Cyanogen combines with hydrogen, and produces a triple compound, the Hydrocyanic or Prussic acid. It may be obtained by moistening prussiate of mercury with muriatic acid, and distilling at a low temperature, having surrounded the receiver with ice. A liquid is thus obtained which has a strong pungent odor, very like that of bitter almonds; its taste is acid, and it is highly poisonous. It volatilizes so rapidly as to freeze itself. It reddens litmus. The specific gravity of its vapour, compared with hydrogen, is $12.7$, so that $100$ cubic inches $= 28.375$ grams; detonated with oxygen it gives as results one volume of carbonic acid gas, half a volume of hydrogen, and half a volume of nitrogen, so that it consists of $1$ volume of cyanogen $+ 1$ volume of hydrogen.
Carbon and Sulphur—Sulphuret of Carbon.—This is a liquid obtained by passing sulphur over red-hot charcoal. When pure, it is transparent and colourless. It is very volatile, and has a pungent taste and peculiar fetid odour. It is inflammable, and, when burned with oxygen, produces sulphurous and carbonic acids. It consists of one proportion of charcoal and two of sulphur; $5.7 + 30 = 35.7$.
6. Boron
Is obtained by the action of potassium on boracic acid, which appears to consist of $5.5$ boron $+ 15$ oxygen.
**Tabular View of the Substances described in the First and Second Divisions of Part III., and of their Compounds, showing their Specific Gravities, Representation, Numbers, and Composition.**
| SUBSTANCES | 100 Cub. In. weigh | Specific Gravity compared to Hydrogen. | Air. | Water. | Number. | Composition. | |------------------|--------------------|----------------------------------------|------|--------|---------|-------------| | Oxygen | | | | | 7.5 | | | Chlorine | | | | | 33.5 | | | Euchlorine | | | | | 63.5 | 30 oxy. + 33.5 chl. | | Chloric acid | | | | | 71. | 37.5 oxy. + 33.5 chl. | | Iodine | | | | | 117.75 | | | Oxiodic acid | | | | | 155.25 | 37.5 oxy. + 117.75 iodine. | | Chloriodic acid | | | | | | | | Hydrogen | | | | | 1 | | | Water | | | | | 8.5 | 7.5 oxy. + 1 hy. | | Muriatic acid gas| | | | | 34.5 | 33.5 chl. + 1 hy. | | solution | | | | | 1.21 | 480 vol. of gas. | | Hydriodic acid | | | | | 118.75 | 117.75 iode + 1 hy. | | Nitrogen | | | | | 13 | | | Substances | 100 Cub. In. weigh | Specific Gravity compared to Hydrogen. | Number | Composition | |----------------------------|-------------------|----------------------------------------|--------|----------------------| | Nitrous oxide | 46.125 | 20.5 | 1.5 | 13 nit. + 7.5 oxy. | | Nitric oxide | 31.5 | 14 | 1 | 13 nit. + 15 oxy. | | Nitrous acid | 64.485 | 28.66 | 2.1356 | 13 nit. + 30 oxy. | | Nitric acid | | | | 50.5 | | Hydro-nitric acid | | | | 13 nit. + 37.5 oxy. | | Common air | 30.195 | 13.42 | 1 | 50.5 nit. ac. + 17 w.| | Chloride of nitrogen | | | | 21 oxy. + 79 n. | | Iode of nitrogen | | | | 13 n. + 134 chlo. | | Ammonia | 18. | 8 | .5961 | 13 n. + 3 hy. | | | | | | 670 volumes. | | Chlorate of ammonia | | | | | | Oxidate of ammonia | | | | | | Chloriodate of ammonia | | | | | | Muriate of ammonia | | | | | | Hydriodate of ammonia | | | | | | Nitrite of ammonia | | | | | | Nitrate of ammonia | | | | | | Sulphur | 67.5 | 30 | 2.2354 | 15 sul. + 15 oxy. | | Sulphurous acid | | | | | | Hydro-sulphuro-nitric oxide| | | | | | Sulphite of ammonia | | | | | | Sulphuric acid | | | | | | Hydro-sulphuric acid | | | | | | Glacial sulphuric acid | | | | | | Sulphate of ammonia | | | | | | Sulphurane, or chloride of sulphur | | | | | | Iode of sulphur | | | | | | Sulphuretted hydrogen | 36 | 16 | 1.1922 | 15 sul. + 1 hy. | | Hydroguretted sulphur | | | | | | Hydrosulphuret of ammonia | | | | | | Phosphorus | | | | | | Oxide of phosphorus | | | | | | Phosphorous acid | | | | | | Hydrophosphorous acid | | | | | | Phosphite of ammonia | | | | | | Phosphoric acid | | | | | | Phosphate of ammonia | | | | | | Chloride of phosphorus | | | | | | Bichloride of phosphorus | | | | | | Ammoniaco-bichloride of phosphorus | | | | | | Iode of phosphorus | | | | | | Hydro-phosphoric gas | 27 | 12 | .8942 | P. 10 + hy. 2. | | Phosphuretted hydrogen | 24.75 | 11 | .8196 | P. 10 + hy. 1. | | Sulphuret of phosphorus | | | | P. 20 + sul. 15. | | Carbon (Diamond) | | | | | | Carbonic oxide | 29.7 | 13.2 | .9836 | Carb. 5.7 + oxy. 7.5 | | Phosgene gas | 107.075 | 46.7 | 3.48 | C. o. 13.2 + chl. 33.5| | Carbonic acid | 46.575 | 20.7 | 1.5423 | Carb. 5.7 + oxy. 15. | | Carbonate of ammonia | | | | C. a. 20.7 + am. 16.| | Bicarbonate of ammonia | | | | C. a. 41.4 + am. 16.| | Carburetted hydrogen | 17.325 | 7.7 | .5738 | Carb. 5.7 + hy. 2. | | Bicarburetted hydrogen | 30.15 | 13.4 | .9985 | Carb. 5.7 + hy. 1. | | Olefiant ether | | | | Olef. 13.4 + chl. 33.5| | Cyanogen | 54.9 | 24.4 | 1.818 | Carb. 11.4 + n. 13. | | Chloro-cyanic acid | 65.1275 | 28.95 | 2.1572 | Cy. 24.4 + ch. 33.5. | | Hydro-cyanic acid | 28.575 | 12.7 | .7058 | Carb. 11.4 + azol. 13 + hy. 1. | | Hydro-cyanate of ammonia | | | | Carb. 5.7 + sul. 30. | | Sulphuret of carbon | | | | | | Phosphuret of carbon | | | | | | Boron | | | | | | Boracic acid | | | | | | Hydro-boracic acid | | | | | | Borate of ammonia (Hydro) | | | | | The third division of undecomposed bodies embraces the Metals. Their general properties, and those of their most important compounds, are, with few exceptions, amply detailed in the body of the work. On the present occasion, it will be required to notice those of more recent discovery, and point out the applications of the law of proportions to their various combinations.
Chemists have adopted different principles of subdivision in regard to the metals, sometimes founding them upon their mechanical, and sometimes upon their chemical qualities. In the former case, malleability, ductility, or tenacity, have been selected as leading characters; in the latter, fusibility and the action of heat and air have furnished characters for classification.
In the present state of our knowledge, it seems that the relative attractions of the metals for oxygen may be most usefully and scientifically assumed as the basis of arrangement, and they may be thus classified under five heads.
The first embraces those metals which neither absorb oxygen nor decompose water at any temperature; their oxides are reducible at a heat below redness.
1. Gold. 2. Silver. 3. Platinum. 4. Palladium. 5. Rhodium. 6. Iridium.
The second division contains metals which, when heated to a certain temperature, absorb and retain oxygen; at higher temperatures they again give it off:
1. Osmium. 2. Mercury. 3. Lead. 4. Nickel.
The metals of the third division absorb oxygen even when at a temperature above redness. They are incapable of decomposing water at any temperature.
1. Arsenic. 2. Molybdenum. 3. Chrome. 4. Tungsten. 5. Columbium. 6. Antimony. 7. Uranium. 8. Cerium. 9. Cobalt. 10. Titanium. 11. Bismuth. 12. Copper. 13. Tellurium.
The metals of the fourth division absorb oxygen even at high temperatures, and, when heated to redness, are capable of decomposing water.
1. Iron. 2. Tin. 3. Zinc. 4. Manganese.
The fifth class includes metals which absorb oxygen, and which rapidly decompose water, at all temperatures.
1. Potassium. 2. Sodium. 3. Barium. 4. Strontium. 5. Calcium. 6. Magnesium.
The sixth class includes bodies which, by analogy, are considered metallic, but of which the oxides have not hitherto been reduced.
1. Silicium. 2. Aluminium. 3. Zirconium. 4. Itrium. 5. Glucium.
It appears from this statement that the metals are thirty-eight in number.
If we arrange the metals according to their specific gravities, they stand as follows:
| Metal | Specific Gravity | |----------------|------------------| | Platinum | 21.00 | | Gold | 19.30 | | Tungsten | 17.50 | | Mercury | 13.50 | | Palladium | 11.50 | | Lead | 11.35 | | Silver | 10.50 | | Bismuth | 9.80 | | Uranium | 9.00 | | Copper | 8.90 | | Arsenic | 8.35 | | Nickel | 8.25 | | Cobalt | 8.00 | | Iron | 7.78 | | Molybdenium | 7.40 | | Tin | 7.30 | | Zinc | 7.00 | | Manganese | 6.85 | | Antimony | 6.70 | | Tellurium | 6.10 | | Sodium | 0.972 | | Potassium | 0.865 |
It will be seen, therefore, that the metals include the heaviest and lightest solids. Of the remaining metals, the specific gravities have not been ascertained.
1. Gold.
Gold occurs in nature in a metallic state, alloyed with a little silver or copper; it may be obtained pure by dissolving it in nitro-muriatic acid, evaporating the solution to dryness, redisolving the dry mass in distilled water, filtering, and adding to it a solution of sulphate of iron; a black powder falls, which, after having been washed with dilute muriatic acid and distilled water, affords on fusion a button of pure gold. Pure gold is of a deep yellow colour. It melts at a bright red heat, and, when in fusion, appears of a brilliant green colour. It shows no tendency to unite to oxygen when exposed to its action in a state of fusion; but if an electric discharge be passed through a very fine wire of gold, a purple powder is produced, which has been considered as an oxide.
Oxide of Gold may be obtained by adding a solution of potash to a solution of chloride of gold; the precipitate must be washed first with weak solution of potash, and then with water, and dried at a temperature of 100°. If this be regarded as a protoxide, that is, consisting of 1 proportion of gold + 1 of oxygen, then the number 97 will represent gold, and this oxide will consist of 97 gold + 7.5 oxygen = 104.5.
Chloride of Gold.—When gold in a state of minute division is heated in chlorine, a compound of a deep yellow colour results, which consists of 97 gold + 33.5 chlorine. When acted upon by water, a muriate of gold is produced.
The action of iodine in gold has scarcely been examined.
Nitrate of Gold.—The nitric acid has scarcely any action upon gold, but it readily dissolves the oxide, forming a yellow styptic deliquescent salt.
Fulminating Gold.—This compound is obtained by adding ammonia to a solution of muriate of gold. It is a yellow powder, which, when gently heated, explodes with some violence. The results of its decomposition are metallic gold, water, and nitrogen.
Sulphuret of Gold is procured by passing sulphurated hydrogen through an aqueous solution of muriate of gold. It is a black substance consisting of 97 gold + 30 sulphur.
Phosphuret of Gold is obtained by heating gold leaf with phosphorus, in a tube deprived of air. It is a grey substance of a metallic lustre, and consists of 97 gold + 20 phosphorus.
Silver.
Silver occurs in nature pure, and alloyed with gold, antimony, arsenic, and bismuth—also combined with sulphur, and with chlorine, and in some triple combinations, such as the sulphuret of arsenic and silver, and of antimony and silver.
To obtain pure silver, the metal as it occurs in commerce may be dissolved in nitric acid; solution of common salt is added to that of silver, as long as it causes a precipitate—which is to be washed, dried, and ignited with twice its weight of subcarbonate of potash—a button of pure silver is thus procured.
Silver is a white metal, and when in fusion, very brilliant. It melts at a cherry red heat, and is not oxidized by exposure to air.
Oxide of Silver may be procured by adding a solution of barytes to one of nitrate of silver; a grey powder is precipitated, which, when washed and dried, consists of 102 silver + 7.5 oxygen.
Chloride of Silver is obtained by adding solution of chlorine, or of muriatic acid, to nitrate of silver. It is white, and fusible by a gentle heat into a semi-transparent mass (Luna Cornea). It consists of 102 silver + 33.5 chlorine.
Fulminating Silver is a compound of ammonia and oxide of silver, more violent in its operation than fulminating gold.
Nitrate of Silver.—The nitric acid diluted with 3 or 4 parts of water readily oxidizes and dissolves silver, and by evaporation a crystallized nitrate of silver is obtained, consisting of 109.5 oxide of silver + 50.5 nitric acid.
Sulphuret of Silver is obtained by the action of sulphuretted hydrogen upon an aqueous solution of nitrate of silver; it is of a dark grey colour, and often found in silver mines. It consists of 102 silver + 15 sulphur.
Sulphate of Silver is a white salt which crystallizes in fine needles, very difficultly soluble in water. It is procured by adding nitrate of silver to sulphate of soda, and then falls as a white precipitate. It easily dissolves in sulphuric and nitric acids, and in ammonia. It consists of 109.5 oxide + 37.5 sulphuric acid.
Phosphate of Silver, a pale yellow compound obtained by pouring phosphoric acid into nitrate of silver. It is insoluble in water, but dissolves in phosphoric acid.
Carbonate of Silver is formed by adding solution of carbonate of potash to nitrate of silver. It is of a pale yellow colour, but, like most other salts of silver, blackens when exposed to light. It consists of 109.5 oxide + 20.7 acid.
Cyanuret of Silver.—A white compound obtained by adding prussiate (hydrocyanate) of potash to nitrate of silver.
Borate of Silver.—An insoluble white powder.
Platinum
Is found in small grains in South America, confined to alluvial strata: The pure metal may be obtained by dissolving crude platinum in nitro-muriatic acid, and precipitating by a solution of muriate of ammonia. This first precipitate is dissolved in nitro-muriatic acid, and again precipitated as before. The second precipitate is heated white hot, and pure platinum remains. It is a white metal, extremely difficult of fusion, and unaltered by the joint action of heat and air.
Oxide of Platinum is procured by adding excess of potash to muriate of platinum. It falls as a black powder, composed of 92 metal + 7.5 oxygen.
Chloride of Platinum may be formed by heating the muriate in close vessels. It has not been particularly examined.
Muriate of Platinum is obtained by evaporating the nitro-muriatic solution; it is acrid, deliquescent, and difficultly crystallizable. It forms a triple compound with ammonia, of difficult solubility.
Salphuret of Platinum is formed by heating the finely divided metal with sulphur in close vessels. It is a black, brittle compound, and consists of 92 platinum + 15 sulphur.
The four following metals have been discovered in the ore of platinum by Dr Wollaston and Mr Tennant.
Palladium and Rhodium.
These metals are obtained as follows: Dissolve crude platinum in nitro-muriatic acid, precipitate by sal-ammoniac, and filter. The filtered liquor may contain iron, copper, lead, gold, platinum, palladium, and rhodium. Immerse a plate of iron, which will precipitate all the above metals except iron; digest this precipitate in dilute nitric acid, which will dissolve the lead and copper; then in nitro muriatic acid, which takes up platinum, palladium, and rhodium; add to this solution some common salt, which forms triple compounds with the three metals. Alcohol dissolves two of these, and leaves the triple salt of rhodium; this is to be dissolved in water, and a plate of zinc immersed into the solution, which precipitates metallic rhodium.
Rhodium is characterized by the rose colour of many of its salts. It is not precipitated either by muriate or hydrosulphuret of ammonia.
The triple salts of palladium and of platinum may be decomposed by prussiate of potash, which throws down the former, and from which the metal may be obtained by ignition.
Palladium is a white metal, malleable and ductile.
Iridium.
When the ore of platinum is digested in nitro-muriatic acid, there remains a black powder, which, when alternately acted upon by muriatic acid and soda, is for the most part dissolved. The acid solution contains iridium, and by evaporation and exposure to heat, the metal is obtained. Its colour is that of platinum; it appears almost infusible. Its combinations have not been examined with precision.
Osmium.
Osmium is contained in the alkaline solution just alluded to. It may be obtained by distilling it with a little sulphuric acid. Its oxide passes over dissolved in water, from which solution it may be separated by mercury.
Osmium has a peculiar smell like new bread. Acids do not act upon it. Alcalies readily dissolve it. Tincture of galls added to its solution produces a vivid blue colour.
Mercury.
The principal ore of this metal is the sulphuret, or native cinnabar, from which the mercury is separated by distillation with quicklime, or iron filings.
Mercury is a brilliant white metal, with a tint of blue. It is liquid at all common temperatures, solid at 40°, and gaseous at 670°.
Mercury and Oxygen.—There are two oxides of mercury. 1. The black, or protoxyde, may be obtained by long agitation of the metal in contact with oxygen, or by washing the chloride of mercury (calomel) with hot lime-water. It is insipid, and consists of 190 M + 7.5 oxygen. 2. The red, or peroxide of mercury, is produced by exposing the metal heated nearly to its boiling point to the action of air. It becomes coated with red scales, spangles, and crystals, which consist of 190 mercury + 15 oxygen.
Chlorides of Mercury.—This metal also forms two compounds with chlorine; the chloride or calomel, composed of one proportion of mercury = 190 + one of chlorine = 33.5, and the bichloride or corrosive sublimate, consisting of one proportion of mercury and two of chlorine, or 190 + 67. These compounds, and especially the former, are most important pharmaceutical preparations. In the London Pharmacopoeia, they are very improperly termed submuriate and oxymuriate of mercury.
Chloride of Mercury, or calomel, is produced by exposing to heat, in proper subliming vessels, a mixture of common salt and sulphate of mercury. Upon the large scale, the following are the best proportions: 50 lbs. of mercury are boiled with 70 lbs. of sulphuric acid to dryness in a cast-iron vessel. 62 lbs. of the dry salt are triturated with 40½ lbs. of mercury, until the globules disappear, and 34 lbs. of common salt are then added. This mixture is submitted to heat in earthen vessels, and from 95 to 100 lbs. of calomel are the result. It is to be washed in large quantities of distilled water, after having been ground to a fine powder.
Calomel is a white crystallizable compound, insoluble in water, and unaltered by exposure to air; long exposed to light, it becomes brown.
Bichloride of Mercury, or corrosive sublimate.—When mercury is heated in chlorine, the metal burns with a white flame, and, combining with the gas, produces a white sublimate of bichloride; but the following process is usually adopted for the preparation of this compound: 5 parts of sulphuric acid are boiled with 4 of mercury to dryness; the dry mass is reduced to powder, and mixed with 4 parts of common salt, and 1 of black oxide of manganese. This mixture is put into a glass subliming vessel, and gradually heated to redness. The bichloride rises in the form of a white semitransparent crystalline mass. Corrosive sublimate has a disgustingly nauseous and astringent flavour, and is highly poisonous. At the temperature of 60°, it is soluble in 20 parts of water, and at 212° in about 3 parts. Alcohol dissolves nearly its own weight. With muriate of ammonia it produces a very soluble compound.
Mercury and Iodine produce a compound of a brilliant scarlet colour, or yellow with excess of mercury.
Mercury and Nitric Acid.—The results of the action of nitric acid upon mercury vary with the circumstances under which it has taken place. If excess of mercury be exposed to the action of dilute nitric acid, the metal is protoxidized, and the solution affords white prismatic crystals of an acrid and metallic taste. These are the nitrate of mercury. When put into water they are resolved into supernitrate, which dissolves, and into subnitrate, which is an insoluble yellow powder. The solution of nitrate of mercury furnishes a black precipitate of oxide with solution of potash, and a white precipitate of chloride with solution of common salt.
When nitric acid diluted with 4 parts of water is boiled on mercury, the acid being in excess, the metal is converted into peroxide, and a compound of nitric acid and peroxide of mercury, or an oxynitrate of mercury is formed. By evaporation irregular crystals, of a very acid taste, are obtained, which, by water, are resolved into a soluble superoxynitrate, and into an insoluble yellow suboxynitrate. Mercury and Sulphur.—When these bodies are triturated together, a black powder results called formerly Ethiops mineral. When ten parts of mercury are heated in a matrass with one of sulphur, there is considerable action attended by ignition, and a violet coloured compound results, which affords, by sublimation, a crystalline mass, becoming, when reduced to powder, of a fine red hue. This is Sulphuret of Mercury, Cinnabar, or Vermillion. It is tasteless, insoluble in water, and consists of $190M. + 30S$.
Mercury and Sulphuric Acid.—Sulphate of Mercury is an insoluble white salt, obtained by adding sulphuric acid to a solution of nitrate of mercury. Oxysulphate of Mercury is formed by boiling the metal with the acid; it is peroxidized and dissolved; sulphurous acid is evolved, and a white crystallized mass remains. When this salt is put into water it is resolved into a Superoxyaluminate, and into an insoluble Suboxyaluminate of a yellow colour, and formerly called Turpeth mineral.
Phosphuret of Mercury is formed by heating phosphorus strongly with calomel; it is of a brown colour. Phosphate of Mercury is obtained by adding phosphate of soda to nitrate of mercury; it is white and insoluble in excess of acid. The Oxysphosphate of Mercury is soluble in excess of acid.
Carbonate of Mercury.—Carbonate of potash furnishes a yellow precipitate in solution of nitrate of mercury.
Mercury and Cyanogen.—The compound hitherto called Prussian of Mercury consists, according to M. Gay-Lussac, of 80 mercury + 20 cyanogen. This compound, when distilled with muriatic acid, affords the hydrocyanic (prussic) acid. (See M. Gay-Lussac's Memoir Annales de Chimie, T. 98, p. 144, ann. 1815.)
Lead.
The natural compounds of this metal are very numerous. The most important is the sulphuret, whence the pure metal is chiefly procured. It is also found combined with carbonic, sulphuric, phosphoric, arsenic, molybdic, and chromic acids, and with oxygen and chlorine. To obtain lead perfectly pure, it may be dissolved in nitric acid,—the solution evaporated to dryness,—the dry mass redissolved in water and crystallized,—the crystals heated strongly with charcoal afford the metal quite pure.
Lead is of a bluish white tint,—it melts at 600°, and by the united action of heat and air is readily converted into an oxide.
Oxides of Lead.—There are three oxides of lead. The protoxide (massicot) is the basis of the salts; it may be obtained by heating the nitrate of lead to redness in a close vessel. It is insipid and insoluble in water,—of a pale yellow colour, and when fused crystallizes on cooling in irregular scales (litharge). It is very soluble in potash and soda, and when in fusion it readily dissolves several of the earthy bodies. If it be considered as a protoxide consisting of one proportion of lead and one of oxygen, then the number 97 will represent lead, and it will consist of $97L. + 7.5S$ oxygen.
If the protoxide be exposed to heat and oxygen, it gradually acquires a bright red colour, and is known under the name of Minium, or deutoxide of lead. This oxide, when exposed to nitric acid, is resolved into protoxide, which is dissolved, and into peroxide, which is an insoluble brown substance, consisting of $97L. + 15S$ oxygen. Minium affords on analysis $97L. + 11.25S$ oxygen, and may, therefore, be regarded as a definite compound of the protoxide and peroxide.
Lead and Chlorine.—Chloride of lead. When laminated lead is heated in chlorine, the gas is absorbed, and a chloride of lead results, composed of $97L. + 33.5S$. The same substance is obtained by adding muriatic acid to nitrate of lead; it is white and fusible, and on cooling forms a horn-like substance (plumbum cornu). It dissolves in 22 parts of water at 60°.
Nitrate of Lead—obtained by dissolving the metal in dilute nitric acid, and evaporation. The salt crystallizes in tetraëdra and octoëdra. It is soluble in 8 parts of water at 212°. It consists of $104.5$ oxide of lead + $50.5$ nitric acid.
Lead and Sulphur readily combine and form a sulphuret of lead, composed of $97L. + 15S$.
Sulphate of Lead is a white insoluble compound, containing $104.5$ oxide of lead + $37.5$ sulphuric acid. It is formed by adding dilute sulphuric acid to nitrate of lead.
Phosphate of Lead is a yellow insoluble compound obtained by adding phosphoric acid to nitrate of lead. It consists of $104.5$ oxide + $25S$ acid.
Carbonate of Lead is an important compound, on account of its use in the arts; it is commonly called White Lead. It is formed by adding carbonate of potash to nitrate of lead, when a white precipitate falls, consisting of $104.5$ oxide + $20.7$ carbonic acid.
Nickel.
Nickel is found native, combined with arsenic, and with arsenic acid. It is procured pure by the following process: Dissolve the metal sold under the name of nickel in dilute nitric acid to saturation, and evaporate to dryness; redissolve in water, and add nitrate of lead sufficient to precipitate the arsenic acid; filter, and immerse a plate of iron to separate copper; filter again, and add solution of carbonate of potash; wash the precipitate thus occasioned, and put it, while moist, into liquid ammonia, which dissolves the oxides of nickel and cobalt, leaving impurities to be separated by a filter; add potash to the ammoniacal solution, which precipitates the oxide of nickel, and which, by ignition with charcoal, affords a globule of the pure metal. Nickel is a white metal, which acts upon the magnetic needle, and is itself capable of becoming a magnet. It is very difficultly fusible, but absorbs oxygen readily when heated red-hot.
Oxide of Nickel is obtained by adding potash to the solution of the nitrate—a precipitate falls of a pale green colour, which is a hydrate or compound of oxide of nickel with water,—this heated to redness, affords a grey oxide, consisting of $55.5$ nickel + $15S$ oxygen.
When nickel is heated in chlorine, a chloride re- Nitrate of Nickel is a deliquescent difficultly crystallizable salt. The sulphate may be formed by dissolving the oxide in dilute sulphuric acid; it crystallizes in four-sided prisms of a beautiful grass-green. (For an elaborate account of the combinations of nickel, see Annales de Chimie, 1816.)
Arsenic.
Arsenic exists in nature nearly pure, and frequently occurs combined with other metallic substances.
The pure metal is obtained by heating a mixture of charcoal and white arsenic in a tube or retort,—it sublimes in small brilliant scales. Arsenic is a very inflammable, fusible, and volatile metal, and when heated in contact with the air, produces white fumes of a peculiar alliaceous odour.—It is highly poisonous in all its combinations.
Arsenic and Oxygen combine in two proportions, and produce compounds which have acid properties,—they have consequently been termed the arsenious and arsenic acids.
Arsenious Acid or White Arsenic is chiefly obtained by sublimation from certain ores, especially those of cobalt. It is met with in commerce as a semitransparent brittle body, of an acrid nauseous taste, soluble in 80 parts of water at 60°. The solution reddens vegetable blues,—it is equally soluble in alcohol. It is composed of 45 arsenic + 15 oxygen. It combines with metallic oxides, and produces a class of salts which have been termed arsenites. Some of these are produced by adding the solution of white arsenic to that of the other metallic oxide; others are best formed by adding solution of arsenite of potash to the other metallic salts.
Arsenic Acid is obtained by distilling four parts of nitric acid and one of arsenious acid to dryness. The white mass which remains is more sour and soluble than the white arsenic, and it constitutes a different set of salts, which are called arseniates. It consists of 45 arsenic + 22.5 oxygen.
The arsenious acid forms uncrystallizable compounds with the alkalies. The arsenite of ammonia is easily formed by digesting finely powdered white arsenic in solution of ammonia. The arsenites of potash and soda may be formed in the same way.
The soluble arseniates, on the other hand, are crystallizable. The arseniate of ammonia forms rhomboidal crystals. Neither the salts of gold nor those of platinum furnish any precipitates with the acids of arsenic, nor with the arseniate or arsenite of potash. Silver is precipitated white by arsenite of potash; but the solution of arsenious acid renders solution of nitrate of silver slightly turbid only. Arsenic acid, on the contrary, produces a copious reddish brown precipitate in solution of nitrate of silver, which is arseniate of silver. The arsenious acid forms dirty white precipitates in the solutions of nitrate and oxynitrate of mercury. The arsenic acid produces no precipitate in either, but the arseniate of potash a yellowish precipitate in both.
Nitrate of lead furnishes no precipitate with arsenious acid; but the arsenite of potash forms a white arsenite of lead. The arsenic acid, and the arseniate of potash, added to solution of nitrate of lead, instantly form insoluble white precipitates of arseniate of lead.
The arseniate of nickel is a very pale green precipitate obtained by adding arseniate of potash to nitrate of nickel. The arsenite of nickel has the same appearance.
Arsenic and Chlorine act upon each other with great energy,—the metal burns, the gas is absorbed, and a chloride of arsenic results, having at first the appearance of white fumes, which condense into a thick fluid, volatile and caustic, and which at a low temperature congeals. (Butter of arsenic.) It consists of 45 arsenic + 67 chlorine. When mixed with water it affords muriate of arsenic.
Arsenic and Iodine, when heated together, produce a red sublimate, which, acted upon by water, furnishes hydriodic and arsenic acids.
Arsenic and Hydrogen.—When an alloy of arsenic and potassium is thrown into water, a brown hydruret of arsenic results. When arsenic is presented to nascent hydrogen, as when a mixture of white arsenic and zinc filings is exposed to the action of dilute sulphuric acid, the metal is dissolved by the gas, and we thus obtain the arsenuretted hydrogen gas. It may be collected and preserved over water. The composition, and consequently the specific gravity of this gas, vary,—and no accurate results have hitherto been obtained concerning it. When inflamed in contact with air, it produces white oxide of arsenic and water, and hydruret of arsenic is deposited upon the vessels. When chlorine is allowed to bubble up into this gas standing over water, inflammation frequently occurs,—hydruret of arsenic is deposited, and chloride of arsenic formed. When decomposed, one volume of arsenuretted hydrogen appears to afford 1.5 volumes of hydrogen.
There are two sulphures of arsenic, the one of a bright red colour, called Realgar,—the other yellow, and known in commerce under the name of Orpiment.
The sulphuric acid dissolves the arsenious acid, and forms a difficultly soluble sulphate of arsenic.
Alloys.—With gold, platinum, and silver, arsenic forms brittle compounds of comparatively easy fusion,—it amalgamates with mercury, produces a brittle alloy with lead, and with nickel forms a reddish compound. The latter metal is indeed generally found alloyed with arsenic.
Molybdenum.
The sulphuret is the most common natural compound of this metal. To procure the metal the native sulphuret is powdered and exposed under a red-hot muffle, till converted into a grey powder, which is to be digested in ammonia, and the solution filtered and evaporated to dryness. The residuum is dissolved in nitric acid, reevaporated to dryness, and violently heated with charcoal. The metal is of a whitish grey colour, and of excessively difficult fusion.
Molybdenum and Oxygen, when exposed to heat, and oxygen molybdenum is acidified, a white crystalline sublimate of Molybdic Acid being formed. There are two other compounds with oxygen—the one black, obtained by heating molybdic acid with charcoal; the other blue, and procured by immersing tin in solution of molybdic acid.—The black oxide consists of
\[ 44 \text{ M.} + 7.5 \text{ oxy.} \]
the blue (molybdous acid) \(44 \text{ M.} + 15\).
the white (molybdic acid) \(44 \text{ M.} + 22.5\).
These acids combine with certain bases forming molybdates and molybdites. Molybdate of silver, of mercury, of lead, and of nickel, may be procured by adding molybdic acid to the respective nitrates of those metals.
Sulphuret of Molybdenum is a sectile compound of a metallic lustre, composed of \(44 \text{ M.} + 30 \text{ S.}\)
**Chrome.**
The native combinations of chrome are the oxide, and the chromates of lead and iron.
By violently igniting the oxide with charcoal a white, brittle, and very difficultly fusible metal is obtained.
**Chrome and Oxygen.**—The Oxide of Chrome is of a green colour, and may be procured by exposing chromic acid to a red heat.
**Chromic Acid** may be obtained by digesting native chromate of lead in fine powder, in carbonate of potash. A chromate of potash is produced, to which sulphuric acid is added; by evaporation sulphate of potash and crystals of chromic acid are obtained. Chromic acid is of a red colour, and very soluble in water.
The other combinations of chrome are very imperfectly known.
**Tungsten.**
There is a mineral called Tungsten, which is a native tungstate of lime, and another called Wolfram, consisting of tungstic acid, iron, and manganese. To obtain the metal, either of its oxides are violently ignited with charcoal—in colour it resembles iron—it is hard and brittle.
**Oxides of Tungsten.**—This metal unites in two proportions with oxygen. The black oxide may be obtained by igniting the peroxide with charcoal. Its properties have not been investigated.
The peroxide, or Tungstic Acid, is obtained from native tungstate of lime, which is fused with four times its weight of subcarbonate of potash. The fused mass is dissolved in water, and nitric acid added to the filtered solution which precipitates the tungstic acid. This body is of a yellow colour—it unites with the alcalies, and forms soluble salts.
**Columbium.**
This metal was first discovered by Mr Hatchett in a mineral from North America. It is found combined with the oxides of iron and manganese, and also with yttria, in the minerals called tantalite and yttrio-tantalite. The peroxide of columbium is almost insoluble in nitric and sulphuric acids, but when freshly precipitated it dissolves in oxalic, tartaric, and nitric acids, and very readily in potash.
**Antimony.**
This metal is found native, but its principal ore is the Sulphuret, from which pure antimony may be obtained by the following process: Mix three parts of the powdered sulphuret with two of crude tartar, and throw the mixture by spoonfuls into a red-hot crucible; then heat the mass to redness, and a button of metal will be found at the bottom of the crucible. Reduce this button to fine powder, and dissolve it in nitro-muriatic acid—pour this solution into water, which will occasion the precipitation of a white powder, which is to be mixed with twice its weight of tartar, and exposed to a dull red heat in a crucible. The button now obtained is pure antimony.
Antimony is of a silvery white colour, brittle and crystalline in its ordinary texture. It fuses at 800° Fahrenheit.
**Antimony and Oxygen.**—These bodies form two well defined compounds, the history of which is of great importance to the pharmaceutical chemist.
The Protoxide of Antimony is thus obtained: To 200 parts of sulphuric acid add 50 parts of powdered metallic antimony. Boil the mixture to dryness, wash the dry mass first in water, and then with a weak solution of subcarbonate of potash, a white powder remains, which, when thoroughly washed with hot water, is Protoxide of Antimony.
This protoxide exists in all the active antimonial preparations—in emetic tartar, kermes, glass of antimony, golden sulphuret, &c. It consists of 85 A. + 15 oxygen. It is fusible and volatile at a red heat, decomposed by sulphur and charcoal; and, when acted on by nitric acid, is converted into peroxide.
**Peroxide of Antimony** is procured by acting upon the powdered metal by excess of hot nitric acid. It is of a yellow white, difficulty fusible, and does not form soluble salts with acids. It consists of 85 ant. + 22.5 oxygen. The diaphoretic antimony of old Pharmacopoeiae consisted of this oxide.
**Antimony and Chlorine** combine in one proportion only to produce the chloride of antimony. (Butter of Antimony.) The powdered metal takes fire when thrown into the gas, and a compound, at first liquid, but afterwards concreting, is formed. It may also be produced by the distillation of antimony and bichloride of mercury, or by heating the solution of protoxide of antimony in muriatic acid. It consists of 85 A. + 67 C. When water is added to the chloride of antimony, a mutual decomposition ensues, and protoxide of antimony and muriatic acid result.
**Sulphuret of Antimony** is easily formed by fusing the metal with sulphur. It consists of 85 A. + 30 S.
**Sulphate of Antimony.**—When sulphuric acid is boiled upon finely powdered antimony, the metal is oxidized, and an acid sulphate and a subsulphate of antimony are the results. In both these salts the metal is in the state of protoxide.
**Hydrosulphuretted Oxide of Antimony.**—This compound has long been known under the name of Kerme Mineral. It is commonly prepared as follows: Equal parts of sulphuret of antimony and common potash are fused together; the resulting mass is finely powdered, and boiled in ten times its weight Chemistry of water. The liquor is filtered while hot; and, during cooling, it deposits kermes. The mother liquor of kermes deposits a copious yellowish red precipitate upon the addition of dilute sulphuric acid, which, when washed and dried, is known under the name of golden sulphur of antimony. It is improperly called in the London Pharmacopoeia antimonii sulphuretum precipitatum.
In forming these compounds, the following changes seem to have taken place. The sulphuret of antimony and potash acts upon the water, a portion of which is decomposed; hydrogen is transferred to the alkaline sulphuret to form hydrosulphuret of potash; hydrogen and oxygen unite to the sulphuret of antimony, producing a hydrosulphuretted oxide of that metal (kermes), which remains dissolved in the hot alkaline hydrosulphuret, and of which one portion is precipitated as that solution cools. When dilute sulphuric acid is added, the hydrosulphuret of potash is decomposed, sulphate of potash is formed, and sulphur and sulphuretted hydrogen are liberated; the sulphur falls in combination with the kermes, producing the golden sulphur, or sulphuretted hydrosulphuret.
Uranium.
The oxide and the sulphuret are the principal native combinations of uranium. To obtain the metal from the sulphuret, it is heated in a muffle, and digested in nitro-muriatic acid; the oxide of uranium is precipitable from this solution by potash; and, when exposed to an intense heat with charcoal, it affords the metal. It is grey, and extremely difficultly fusible.
Very few experiments have hitherto been made upon this metal. The oxide precipitated from its nitric solution by alcalies is yellow, but by heating with charcoal it becomes black. The uranitic ore, called by the Germans Uran glimmer, is a hydrate of the yellow oxide. The salts of uranium have a yellow colour and an astringent metallic taste. Potash forms in their solutions a yellow precipitate, and carbonate of potash a white precipitate; both these precipitates are redissoluble in excess of alcali.
Cerium.
This metal has been obtained by Hisinger and Berzelius from a mineral found at Bastnas in Sweden, to which they have given the name of cerite. The ore is calcined, pulverised, and digested in nitro-muriatic acid. To the filtered solution, saturated with potash, oxalic acid is added, which occasions a precipitate; this, when dried and ignited, is oxide of cerium.
There are two oxides of cerium, the red or protoxide, and the white or peroxide. The salts of cerium have a sweetish taste. Those formed with the protoxide are colourless, those with the peroxide are yellow.
Cobalt.
The native combinations of cobalt are the oxide, the compound of the metal with iron, nickel, arsenic, and sulphur. It is also found combined with arsenic acid.
To obtain the pure metal, the substance called zaffre, which is an impure oxide of cobalt, may be Chemistry detonated three or four times with half its weight of nitre, then washed in hot water, and the residue digested in nitric acid. The nitric solution, when filtered and evaporated, yields an oxide, which, by ignition with charcoal, affords cobalt. Cobalt is of a grey colour, brittle, and difficultly fusible.
Cobalt and Oxygen unite in two proportions. The protoxide is formed by adding potash to the nitrate, and drying the precipitate; it appears reddish black. By exposure to heat and air, it absorbs an additional portion of oxygen, and is thus converted into black peroxide. The protoxide, when recently precipitated and moist, is blue; and, if left in contact of water, becomes a red hydrate.
Cobalt, when heated in chlorine, burns; but the chloride of cobalt has not been examined.
The salts of cobalt all contain the protoxide, and are of a red colour; the alcalies produce in them bluish precipitates, which redissolve in excess of ammonia. Prussiate of potash forms a grass-green precipitate; and phosphoric, carbonic, arsenic, and oxalic acids, form insoluble precipitates of a red colour.
Muriate of Cobalt is a deliquescent salt, of a blue green colour; when a little diluted, it becomes pink; the pale pink solution, when written with, is scarcely visible; but, if gently heated, the writing appears in brilliant green, which soon vanishes as the paper cools, in consequence of the salt absorbing the aerial moisture.
With nitric acid, the oxide of cobalt furnishes a red deliquescent nitrate of cobalt.
Sulphuret of Cobalt is formed by heating the oxide with sulphur.
Sulphate of Cobalt forms red rhombic crystal.
Phosphuret of Cobalt is a white brittle compound.
Phosphate of Cobalt may be formed by double decomposition, as by adding phosphate of soda to muriate of cobalt; it is insoluble; of a purple colour; and, if mixed with eight parts of gelatinous alumina, and heated, it produces a beautiful blue, which may sometimes be employed by painters as a substitute for ultramarine.
Titanium.
Titanium exists in the state of oxide, in two minerals—in tititanite and in menachanite. The metal may be obtained from the former by fusion with potash; the fused mass, washed with water, leaves oxide of titanium, containing a little iron; it is to be dissolved in muriatic acid, and precipitated by oxalic acid. The oxalate affords the metal by intense ignition with charcoal.
Titanium is of the colour of copper. It is oxidized by exposure to heat and air, and is said to be susceptible of three degrees of oxidization, the colours of the oxides being blue, red, and white.
Bismuth
Is found native, combined with oxygen, and with arsenic and sulphur. The metal may be obtained pure by dissolving the bismuth of commerce in nitric acid; water is added to the nitric solution, which separates oxide of bismuth. This oxide is easily re- Bismuth is a brittle brilliant white metal, with a slight tint of red; it fuses at 476°, and always crystallizes on cooling. When exposed to heat and air it oxidizes, forming the white oxide. It consists of 66.5 bismuth + 7.5 oxygen.
Chloride of Bismuth is procured by heating the metal in the gas. It is a fusible volatile substance, decomposed by water; consisting of 66.5 B + 33.5 C.
Nitrate of Bismuth crystallizes in small four sided prisms, consisting of 74 oxide + 50.5 acid. It is decomposed by water, and the oxide of bismuth is thrown down in the form of fine white powder. (Magistery of Bismuth, Pearl white, &c.)
Sulphuret of Bismuth is of a bluish colour and metallic lustre; it consists of 66.5 B + 15 sulphur.
Sulphate of Bismuth consists of 74 oxide + 37.5 acid; it is a white compound insoluble in, but decomposed by water, which converts it into a subsulphate and supersulphate.
Bismuth forms alloys, some of which are remarkable for their fusibility. With gold, platinum, and silver, it forms brittle compounds. A compound of 8 parts of bismuth, 5 of lead, and 3 of tin, liquefies at 212°; it is called fusible metal. The addition of 1 part of quicksilver renders it yet more fusible.
Copper.
This metal is found native, and in various states of combination. Of its ores, the oxide, chloride, sulphuret, sulphate, phosphate, carbonate, and arseniate, are the most remarkable. The metal may be obtained perfectly pure by dissolving the copper of commerce in muriatic acid; the solution is diluted, and a plate of iron is immersed upon which the copper is precipitated; it may be fused into a button.
Copper has a fine red colour and much brilliancy; it is very malleable and ductile, and has a peculiar smell when warmed or rubbed. It melts at a cherry red or dull white heat.
Copper and Oxygen.—There are two oxides of copper. The red or protoxide occurs native. It may be formed artificially, by dissolving a mixture of metallic copper, and peroxide of copper, in muriatic acid. When potash is added to this solution, a hydrated protoxide of an orange colour falls; if quickly dried out of the contact of air, it becomes of a red brown; it consists of 60 copper + 7.5 oxygen. The peroxide of copper is procured by precipitating nitrate of copper by potash, washing the precipitate, and exposing it to a red heat. It is black, and consists of 60 copper + 15 oxygen.
Copper and Chlorine.—Gaseous chlorine acts upon copper with great energy, and produces two chlorides, the one a fixed fusible substance, which is the chloride, consisting of 1 proportion of copper = 60 + 1 proportion of chlorine = 33.5. The other a volatile yellow substance, which is a bichloride, and contains 60 copper + 67 chlorine. These compounds furnish, with water, a solution of nitrate of copper.
Nitric Acid, diluted with three parts of water, rapidly peroxidizes copper, forming a bright blue solution, which affords deliquescent prismatic crystals or evaporation. It consists of 75 oxide + 50.5 acid. Potash forms, in this solution, a bulky blue precipitate of hydrated peroxide of copper.
If ammonia be added to solution of nitrate of copper, it occasions also a precipitate of hydrate, but if it be added in excess, the precipitate is redissolved, and a triple compound produced. Ammonia also dissolves the peroxide of copper; forming a crystalizable compound of an intense blue colour.
Copper and Sulphur.—There are two sulphurets of copper, both of which exist native; the one is black, and may be formed artificially, by heating a mixture of copper filings and sulphur; as soon as the latter melts a violent action ensues, the copper becomes red hot, hydrogen escapes, and a black brittle body is formed, consisting of 60 copper + 15 sulphur.
The Bisulphuret is a common ore of copper called Pyrites. It consists of 60 copper + 30 sulphur, and is of a golden yellow colour.
Copper and Sulphurous Acid—Sulphite of Copper may be obtained by passing sulphurous acid into water, through which peroxide of copper is diffused. Small red crystals are formed, composed of protoxide of copper and sulphurous acid.
Copper and Sulphuric Acid—Oxysulphate of Copper—Blue Vitriol.—This salt is formed by dissolving peroxide of copper in sulphuric acid; it crystallizes in rhomboidal prisms of a fine blue colour. It is produced upon a large scale, by exposing roasted sulphuret of copper to air and moisture. It consists of 75 peroxide + 75 sulphuric acid; when crystallized, it contains 5 proportions of water, and consequently its composition will stand thus:
| Proportion | Composition | |------------|-------------| | 1 proportion peroxide | 75 | | 2 proportions sulphuric acid | 75 | | 5 proportions of water | 42.5 |
192.5
By cautiously adding ammonia to a solution of the foregoing salt, a subsulphate of copper is precipitated, consisting of 150 oxide + 37.5 acid. The alcalies precipitate hydrated peroxide from the solution of this salt, and excess of ammonia forms a triple sulphate.
Phosphorus and Copper form a grey brittle phosphuret.
Phosphate of Copper may be formed by mixing solution of sulphate of copper with phosphate of soda; it is a blue green insoluble powder, composed of 75 oxide + 25 acid.
Carbonate of Copper, artificially prepared by adding carbonate of potash to sulphate of copper, is a green insoluble compound, containing 75 oxide + 20.7 acid. Verditer is a mixture of this carbonate with chalk; it is obtained by adding chalk to solution of nitrate of copper.
Many of the alloys of copper are important. With gold it forms a fine yellow ductile compound, used for coin and ornamental work. Sterling or standard gold consists of 11 gold + 1 copper. The specific gravity of this alloy is 17.157. With silver it forms a white compound, used for plate and coin. Lead and copper require a high red heat for union—the alloy is grey and brittle. Tellurium.
The ores of tellurium are, 1. Native, in which the metal is combined with iron and a little gold. 2. Graphic ore, which consists of tellurium, gold, and silver. 3. Yellow ore, a compound of tellurium, gold, lead, and silver; and 4. Black ore, consisting of the same metals with copper and sulphur.
The metal is extracted from these ores by precipitating their diluted nitro-muriatic solution by potash, which is added in excess; the clear liquor is poured off and saturated with muriatic acid, which affords a precipitate of oxide of tellurium. This heated in a glass retort with charcoal furnishes the metal. Tellurium is of a bright grey colour, brittle, easily fusible, and very volatile. It burns with a blue flame, and produces a yellowish oxide, composed of $37 \text{ tell.} + 7.5 \text{ oxy.}$
Chloride of Tellurium is white, and consists of $37 \text{ T.} + 33.5 \text{ C.}$
Tellurium combines with hydrogen, producing Telluretted hydrogen gas. The soluble salts of tellurium furnish white precipitates, when neutralized by alcalies, which are soluble in excess either of the solvent or precipitant.
Iron.
The most important native combinations of iron, whence the immense supplies for the arts of life are drawn, are the oxides. Iron is also found combined with sulphur, and with several acids; it is so abundant that there are few fossils free from it. It is also found in some animal and vegetable bodies. Iron is a metal of a blue white colour, very malleable and ductile, and fusible at a white heat.
Iron and Oxygen.—Exposed to heat and air, iron quickly oxidizes. It unites with oxygen in at least two proportions. The protoxide may be procured by precipitating a solution of sulphate of iron by potash, washing the precipitate out of the contact of air, and drying it at a red heat. It is black, and consists of $52 \text{ iron} + 15 \text{ oxygen.}$
When this oxide is boiled in nitric acid, and precipitated by ammonia, washed, and dried at a low red heat, it increases in weight, and acquires a brown colour. This is the peroxyde composed of $52 \text{ iron} + 22.5 \text{ oxygen.}$ These oxides form distinct salts with the acids. The salts containing the black oxide are of a green colour, mostly crystallizable, become reddish brown by exposure to air, are insoluble in alcohol, and their solutions absorb nitric oxide gas and become of a deep olive colour.
The salts with the brown oxide do not crystallize; they are brown, soluble in alcohol, and do not absorb nitric oxide.
The alcalies precipitate hydrated oxides from these solutions.
Iron and Chlorine unite in two proportions—the chloride may be obtained by evaporating green muriate of iron to dryness, and exposing the residuum to a red heat. A grey brittle substance is formed, consisting of one proportion of iron and two of chlorine $52 + 67.$
When iron wire is heated in chlorine it burns with a red light, and produces a compound which rises in beautiful brown scales. It is the perchloride of iron, and consists of one proportion of iron and three of chlorine $52 + 100.5.$ The chloride and perchloride of iron produce muriate and oxymuriate of iron when acted upon by water. These salts are both deliquescent and uncrystallizable.
Iodine and Iron readily form a brown compound, fusible at a red heat, and which, when put into water, forms a hydriodate of a green colour.
The nitric acid dissolves the protoxide and peroxide of iron, and produces a green nitrate and a red oxynitrate, neither of which are crystallizable.
Sulphur and Iron.—There are two sulphurets of iron—the black sulphuret is composed of $52 \text{ iron} + 30 \text{ sulphur;}$ and the yellow sulphuret, or bisulphuret, of $52 \text{ iron} + 60 \text{ sulphur.}$ The former compound is produced by melting sulphur with iron filings; it exists in nature under the name of magnetic pyrites—the bisulphuret is exclusively a natural product, very abundant, and called iron pyrites.
Sulphates of Iron.—The sulphuric acid with the protoxide of iron forms a salt which crystallizes in green rhomboidal prisms, of a stypic taste, soluble in twice their weight of cold water. This salt is called Copperas or green vitriol, and is often prepared by exposing roasted pyrites to moisture. It consists of one proportion of protoxide $= 67 +$ two proportions of acid $= 75.$ The oxysulphate of iron is obtained by dissolving the moist red oxide in dilute sulphuric acid—it does not crystallize, but affords, by evaporation, a red deliquescent mass, consisting of 1 oxide $+ 3$ sulph. acid or $74.5 \text{ oxide} + 112.5 \text{ sul. acid.}$ It is formed in the mother waters of the sulphate.
Phosphuret of Iron may be formed by dropping phosphorus into a crucible containing red-hot iron wire; it is a brittle grey compound, and acts upon the magnet.
Phosphates of Iron.—These are both insoluble, and may be formed by adding solution of phosphate of soda to sulphate and oxysulphate of iron. The phosphate of iron is of a pale blue colour; the oxysphosphate is white.
Iron and Carbon.—The different kinds of cast iron contain more or less carbon, which materially affects their properties. Steel and plumbago are carburets of iron.
Carbonic Acid may be combined with the protoxide of iron, by adding carbonate of potash to sulphate of iron; a green precipitate of carbonate of iron falls, which, exposed to air, becomes brown, and evolves carbonic acid.
Hydrocyanic (Prussian) Acid may be united by double decomposition with the oxides of iron, as by adding the prussiate of potash to the sulphate and oxysulphate. The former affords a white, the latter a fine blue precipitate, of hydrocyanate or prussiate of iron. (Prussian blue.)
The alloys of iron, with the metals hitherto described, are not important.
Tin.
The native oxide is the principal ore of tin; the metal is obtained by heating it to redness with charcoal. Tin has a silvery white colour; it is malleable, though sparingly ductile. It melts at $440^\circ,$ Zinc.
Zinc is found in the state of oxide and of sulphuret. It may be obtained pure by dissolving the zinc of commerce in dilute sulphuric acid, and immersing a plate of zinc for some hours in the solution, which is then filtered, decomposed by subcarbonate of potash, and the precipitate ignited with charcoal.
Zinc is a bluish white metal, malleable at 300°, but very brittle when its temperature approaches the point of fusion, which is about 680°.
Oxide of Zinc is obtained by heating the metal exposed to air. At a red heat it inflames, burns with a bright flame, and is converted into a white flocculent substance, formerly called Pompholix, nihil album, and Philosopher's wool. It consists of 33 zinc and 7.5 oxygen. This oxide is white, tasteless, and soluble in the alkalies.
Chloride of Zinc is formed by heating leaf zinc in chlorine. It is a volatile fusible compound, producing a muriate of zinc by the action of water. It consists of 33 zinc + 33.5 chlorine.
Iodine and Zinc readily combine, and produce a fusible, volatile, and crystalline compound, which, when exposed to air, deliquesces into hydriodate of zinc.
Sulphuret of Zinc exists native under the name of Blende. It may be formed artificially by heating oxide of zinc with sulphur, and is then of a yellow brown colour. It consists of 33 zinc + 15 sulphur.
Sulphate of Zinc.—The metal is readily oxidized and dissolved by dilute sulphuric acid, hydrogen gas is given off, and a transparent colourless solution of sulphate of zinc results, which, by evaporation, affords crystals in the form of four-sided prisms, terminated by four-sided pyramids.
This salt is soluble in 2.5 parts of water at 60°. It consists of 1 proportion of oxide = 40.5 + 1 proportion of acid = 37.5. Its crystals contain 7 proportions of water = 59.5. Sulphate of zinc is prepared for the purposes of the arts from the native sulphuret, and is usually in the form of a white amorphous mass called white vitriol.
Phosphuret of Zinc is a brilliant lead-coloured compound.
Phosphate of Zinc is not crystallizable. It may be obtained by dissolving zinc in phosphoric acid and evaporation to dryness.
Carbonate of Zinc occurs native, forming one of the varieties of calamine.
Zinc forms with copper the very useful alloy called brass.
Manganese.
The common ore of manganese is the black or peroxide, which is found native in great abundance.
The metal may be procured by exposing the protoxide mixed with charcoal to an intense heat. It is of a bluish white colour, very brittle, and difficult of fusion. When exposed to air, it becomes an oxide.
Manganese and Oxygen.—There are two definite oxides of manganese. The protoxide may be obtained by digesting the native black oxide in muriatic acid. Chlorine is abundantly evolved, and the hydrogen of the muriatic acid unites with part of the oxygen of the oxide to produce water. The metal thus partly deoxidized, is dissolved by the remaining muriatic acid, forming a muriate of manganese. Iron is almost always present, which may be easily separated by neutralizing the muriatic solution with ammonia. The oxide of iron is directly precipitated, but the oxide of manganese remains in solution, and may be separated by excess of ammonia.
The solutions of manganese furnish a white precipitate with the alkalies, which is a hydrated oxide of manganese, and which, when dried in close vessels, acquires a deep olive colour, and is the protoxide. It consists of $56.5$ manganese + $15$ oxy. and the hydrate contains $71.5$ oxide + $17$ water.
When this oxide is heated in contact with oxygen, it becomes deep brown, and is thus converted into the peroxide, which consists of $36.5$ mang. + $22.5$ oxygen. This peroxide is not soluble in acids.
Manganese and Chlorine.—By burning the metal in chlorine, or by exposing muriate of manganese to a strong heat, a pink semitransparent flaky substance is obtained, consisting of $56.5$ M. + $67$ C.
Manganese and Sulphur appear unsusceptible of combination.
Sulphate of Manganese is formed by dissolving the protoxide in the acid, or by boiling in it the peroxide, in which case oxygen is evolved. There are two sulphates. The one which is neutral is of a pink colour, the other, acid, is white. They crystallize in rhombooidal prisms.
Phosphuret of Manganese is of a blue white metallic lustre, and considerably inflammable.
Phosphate of Manganese is precipitated in the form of a white insoluble powder, by adding phosphate of soda to muriate of manganese.
Carbonate of Manganese is white, insipid, and insoluble in water.
Potassium.
The body known under the name of caustic potash is a hydrated oxide of this metal. It is decomposed at a white heat by the action of iron in the following manner: A sound and perfectly clean gun-barrel is bent, as shown in the annexed sketch. It is then covered with an infusible lute between the letters O and E (fig. 1.), and the interior of the luted part is filled with clean iron turnings. Pieces of fused potash are then loosely placed in the barrel between E and C. AA is a copper tube and small receiver which are adapted to the extremity O, and to each other, by grinding. This apparatus is next transferred to the furnace, arranged, as shown in fig. 2. X and T representing two glass tubes dipping into mercury. The furnace is supplied with air by a good double bellows entering at B, and a small wire basket (G) is suspended below the space E.C. The part of the barrel in the furnace is now cautiously raised to a white heat, and the escape of air by the tube X shows that all is tight. Some burning charcoal is then put at the end (E) of the cage G, which causes a portion of potash to liquefy and fall into the low part of the barrel upon the iron. Hydrogen gas instantly escapes by the tube X, and attention must now be had to keep the copper tubes (AA) cool, by laying wet cloths upon them. When the evolution of gas ceases, fresh charcoal is placed under the potash, and so on till the whole has passed down; if too much potash be suffered to fall at once, the extrication of gas at X will be very violent, which should be avoided. If the space between A and O should become stopped by potassium, gas will issue by the tube T (which must always be under a greater pressure of quicksilver than the tube X), and it may be fused by applying hot charcoal to the tube, when the gas will again appear at X and cease at T. When the operation is concluded, the tubes X and T are removed, and corks quickly applied to the holes; and when the apparatus is cool, the barrel is carefully removed from the furnace, and a little naphtha suffered to run through the barrel. The potassium is found in globules in the tube and receiver AA, and considerable portions often lodge at O. The success of this operation is certain, if the heat has been sufficient; but the barrel, if not very carefully covered with lute, is apt to melt, and much, if not the whole, of the product is lost.*
Potassium is a white metal of great lustre. It instantly tarnishes by exposure to air. It is ductile and of the consistency of soft wax. At $150^\circ$ it enters into perfect fusion; and at a bright red heat rises in vapour. At $32^\circ$ it is a hard and brittle solid. If heated in air it burns with a brilliant white flame.
Potassium and Oxygen.—When potassium is thrown into water it instantly takes fire,—hydrogen gas is evolved, and oxide of potassium or potash is found dissolved in the water. The quantity of hydrogen evolved in this experiment, becomes the indicator of the proportion of oxygen which has been transferred to the metal; 100 parts of potassium are thus found to absorb 20 of oxygen; and if this be considered a protoxide, then $20 : 100 :: 7.5 : 37.5$,—so that $37.5$ will be the number representing potassium, and $37.5$ P. + $7.5$ O. = $45$ will represent
* The discovery of the nature of the alkalies, the most brilliant of modern chemistry, was made by Sir H. Davy in the year 1807, and was the result of his laborious electro-chemical researches, of which the commencement and progress are detailed in his various communications to the Royal Society. dry oxide of potassium. Potash in the state it is usually met with in laboratories, contains a considerable portion of water, from which it may be freed by the action of iron at high temperatures, and there always remains in the barrel, after the above experiment, a large portion of dry potash. It is a hard grey substance which, by water, is slowly converted into the hydrated oxide, or caustic potash, which may be obtained by evaporation to dryness. This substance, after exposure to a red heat, is white and very soluble in water; it may be considered as a compound of 1 proportion of protoxide of potassium \(=45+1\) proportion of water \(=8.5\), and its number \(=53.5\).
Peroxide of Potassium.—If the metal be heated in considerable excess of oxygen, it burns with intense heat and light, and an orange coloured substance is obtained, which consists of \(37.5\) potassium \(+22.5\) oxygen \(=60\). This peroxide of potassium, when put into water, effervesces, oxygen is given off, and a solution of the hydrated protoxide is obtained.
The hydrated protoxide, or caustic potash, is procured in our laboratories by decomposing its subcarbonate by lime. It is often cast into sticks for the use of surgeons, who employ it as a caustic, and in this state it generally contains some peroxide, and therefore evolves oxygen when dissolved in water. It may be further purified by the action of alcohol, which dissolves the pure hydrate, and leaves earthy and other impurities—the alcohol is then driven off by heat.
Hydrate of Potassa thus purified is white,—very acid and corrosive, and at a red heat evaporates in the form of white acid smoke. It quickly absorbs moisture from the air, and at \(60^\circ\) one part of water dissolves two. It may be crystallized in octocidrons.
Chlorine and Potassium act very energetically on each other, and produce the white compound which has been called Muriate of Potash, but which is a true chloride of potassium, consisting of \(37.5\) P. \(+33.5\) Ch. It is soluble without decomposition in three parts of water at \(60^\circ\). When potassium is heated in gaseous muriatic acid, this compound is formed, and hydrogen is evolved.
Chlorate of Potash is formed by passing chlorine through a solution of potash. Chloride of potassium is one of the results, the other is a salt in brilliant rhomboidal tables (formerly called Oxyuriate of Potash), the chlorate. When exposed to heat it gives out oxygen, and chloride of potassium remains. It is soluble in 18 parts of cold and 2.5 of boiling water. It acts very energetically upon many inflammables, and triturated with sulphur, phosphorus, and charcoal, produces inflammation and explosion. It consists of one proportion of chloric acid and one of potash, or \(71\) C.A. \(+45\) P. Its ultimate components, therefore, are
\[ \begin{align*} 6 \text{ proportions of oxygen}, & \\ 5 \text{ in the acid and } 1 \text{ in the alcali}, & \\ 1 \text{ proportion of chlorine}, & \\ 1 \text{ potassium}, & \\ \end{align*} \]
\(=45\)
Iode of Potassium.—Iodine and potassium act up on each other very energetically, and a crystalline compound is obtained, white, fusible. The hydriodic acid and potash produce a similar compound.
When iodine is put into solution of potash, the results are iodate of potash and iode of potassium.
Potassium and Hydrogen.—When potassium is heated in hydrogen, it absorbs a portion of the gas, and produces a grey and highly inflammable hydruret. When hydrogen and potassium are passed together through a white hot tube, the gas dissolves the metal, and produces a spontaneously inflammable potassiucretted hydrogen gas. Both these compounds are usually formed, during the operation for obtaining potassium by the gun-barrel.
Nitrate of Potash—Nitre—Saltpetre.—This salt is an abundant natural product, and is principally brought to this country from the East Indies. It crystallizes in six-sided prisms, usually terminated by dihedral summits; it dissolves in 7 parts of water at \(60^\circ\), and in its own weight at \(212^\circ\). Its taste is cooling and peculiar. It consists of 1 proportion of acid \(=50.5+1\) proportion of potash \(=45\). Or of
\[ \begin{align*} 6 \text{ proportions of oxygen}, & \\ 5 \text{ in the acid and } 1 \text{ in the alcali}, & \\ 1 \text{ proportion of nitrogen}, & \\ 1 \text{ potassium}, & \\ \end{align*} \]
\(=95.5\)
When exposed to a white heat, it is decomposed into oxygen, nitrogen, and potash. It fuses at a heat below redness, and congeals on cooling into cakes called sal prunelle. It is rapidly decomposed by charcoal at a red heat. The products of the combustion of a mixture of charcoal and nitre, are carbonic acid and nitrogen gases, and subcarbonate of potash. It is also decomposed by sulphur (see Sulphuric Acid), and by phosphorus.
This is a highly important salt, as constituting the basis of gunpowder. It is also largely employed as a source of nitric acid. (See Nitric Acid.)
Potassium unites to Sulphur with the evolution of much heat and light, and produces a red compound.
Potash and Sulphur, when fused together, form a red sulphuret of potash. (Liver of Sulphur.) Its taste is bitter and acid. It is very soluble in water, forming a yellow solution of hydrosulphuret of potash. The action of the sulphuret of potash on water is complicated, and has been variously explained. By some this is considered as a compound of potassium and sulphur; in which case, when acted upon by water, hydrogen is imparted to the sulphur, and oxygen to the potassium; and a sulphuret of potash with excess of sulphur (or sulphuretted sulphuret of potash) is formed. If we consider the sulphuret as consisting of potash and sulphur, then the oxygen, as well as the hydrogen, of the water, must be transferred to the sulphur, and sulphuric and sulphurous acid, and sulphuretted hydrogen, would be formed; and generally when the solutions of the livers of sulphur are examined, sulphate and sulphite of the alcali are found. On the whole, however, it appears most probable, that when sulphur and the alcalies are fused together at a high temperature, the latter un- Chemistry.
Sulphite of Potash is formed by passing sulphurous acid into a solution of potash, and evaporating out of the contact of air. Rhomboidal plates are obtained, white, of a sulphurous taste, and very soluble. By exposure to air, they pass into sulphate of potash.
Sulphate of Potash is the result of several chemical operations carried on upon a large scale in the processes of the arts. It may be formed directly by saturating sulphuric acid by potash. It crystallizes in short six-sided prisms, terminated by six sided pyramids. The body of the prism is often wanting, and the triangular faced dodecaedron results. This salt dissolves in 16 parts of cold, and 5 of boiling water. It consists of
\[ \frac{1 \text{ proportion of acid}}{1 \text{ alcali}} = \frac{37.5}{45} = 82.5 \]
Supersulphate or Bisulphate of Potash is formed by adding sulphuric acid to a hot solution of sulphate of potash. The first crystals which form are in delicate needles of an acid taste, soluble in 2 parts of water at 60°, and consist of
\[ \frac{2 \text{ proportions of acid}}{1 \text{ potash}} = \frac{75}{45} = 120 \]
Phosphuret of Potassium is a brown compound, which rapidly decomposes water, producing phosphuretted hydrogen gas, and hydrophosphuret of potash.
Phosphite of Potash is a soluble deliquescent uncrystallizable salt.
Phosphate of Potash is a soluble difficultly crystallizable salt. Superphosphate of potash crystallizes in four-sided prisms.
Potash and Carbonic Acid.—These bodies combine in two proportions, forming the subcarbonate and the bicarbonate of potash.
Subcarbonate of Potash is a salt of great importance in many arts and manufactures, and is known in commerce in different states of purity under the names of wood ash, potash, and pearl ash.
It may be obtained directly by passing carbonic acid into a solution of potash, evaporating to dryness, and exposing the dry mass to a red heat; or by burning tartar, whence the name salt of tartar has been applied to it. This salt is fusible without decomposition, at a red heat; it is very soluble in water, and deliquesces by exposure to air, forming a dense solution, once called oil of tartar per deliquium. Its taste is alcaline, and it renders vegetable blues green. It consists of
\[ \frac{1 \text{ proportion acid}}{1 \text{ potash}} = \frac{20.7}{45} = 65.7 \]
Bicarbonate of Potash is formed by passing a current of carbonic acid into a solution of the subcarbonate. By evaporation crystals are obtained in the form of four-sided prisms, with dihedral summits. Their taste is only slightly alcaline, and they require for solution 4 parts of water, at 60°. Exposed to a red heat, carbonic acid is evolved, and subcarbonate of potash remains. This bicarbonate consists of
\[ \frac{2 \text{ proportions of carbonic acid}}{1 \text{ potash}} = \frac{41.4}{45} = 86.4 \]
Arseniate of Potash is formed by heating together white oxide of arsenic and nitrate of potash. It crystallizes in four sided prisms.
Chromate of Potash is obtained by digesting chromate of lead in a solution of potash. The salt crystallizes in rhomboidal prisms of a yellow colour.
Sodium.
Sodium is obtained from soda by an operation analogous to that for procuring potassium from potash. In colour it resembles lead, it fuses at 180°, and is volatile at a white heat. It burns when heated in contact with air, and requires the same cautions to preserve it as potassium.
Sodium and Oxygen.—When sodium is thrown upon water, it produces violent action, but the metal does not in general inflame; hydrogen is evolved, and a solution of soda is procured. By the quantity of hydrogen evolved, we learn that soda (protoxide of sodium) consists of about 74.6 sodium and 25.4 oxygen per cent.; and, if soda be considered as the protoxide, the number representing the metal will be 22, and soda will consist of 22 S. + 7.5 O., and be represented by 29.5. By heating sodium in oxygen, an orange-coloured oxide is formed, consisting of 22 S. + 11.25 O., and which, by the action of water, evolves oxygen, and produces a solution of the protoxide.
Soda, as it usually occurs in the laboratories, is obtained from the subcarbonate by the action of lime and alcohol, as described under the head Potash. It consists of 29.5 oxide of sodium + 8.5 water, and is represented by 38. When soda is exposed to air, it soon becomes covered with an efflorescence of subcarbonate of soda.
Chloride of Sodium.—Sodium, when heated in chlorine, burns, and produces a white compound, of a pure saline flavour, soluble in 23 parts of water at 60°, and forming cubic crystals. It has all the properties of common salt, or muriate of soda, and consists of
\[ \frac{1 \text{ proportion of chlorine}}{1 \text{ sodium}} = \frac{33.5}{22} = 55.5 \]
This compound is decomposed, when heated with potassium. Sodium and chloride of potassium are the results.
When soda is heated in chlorine, oxygen is evolved; when heated in muriatic acid, water is formed; and in both cases chloride of sodium is the product.
Sodium and Iodine act upon each other with the same phenomena as potassium. Nitrate of Soda crystallizes in rhombs, soluble in three parts of water at 60°.
Sulphuret of Sodium and of Soda. (See Potassium.)
Sulphite of Soda is crystallizable in transparent four and six sided prisms, soluble in four parts of water at 60°.
Sulphate of Soda—Glauber's Salt—is abundantly produced in the manufacture of muriatic acid by the action of sulphuric acid upon common salt.
Common salt consists of 22 sodium + 33,5 chlorine. Sulphuric acid consists of 37,5 dry acid + 8,5 water. The water of the acid, consisting of 1 hydrogen + 7,5 oxygen, is decomposed. Its hydrogen is transferred to the chlorine to produce gaseous muriatic acid (= 1 H. + 33,5 C. = 34,5 Mur. A.), and its oxygen unites to the sodium, forming dry soda (= 7,5 Ox. + 22 S. = 29,5 soda). The 37,5 dry acid then unite to the 29,5 soda, to produce sulphate of soda, which will be represented by the number 67. Sulphate of soda crystallizes from its aqueous solution in large four-sided prisms transparent, and efflorescent, when exposed to air. They consist of 67 dry sulphate + 85 water.
Phosphate of Soda crystallizes in rhomboidal prisms, soluble in three parts of water at 60°, and efflorescing when exposed. It consists of
- 29,5 soda. - 25 phosphoric acid.
54,5
Subcarbonate of Soda is chiefly obtained by the combustion of marine plants. It consists of
- 29,5 soda. - 20,7 carbonic acid.
50,2
Its crystals contain 7 proportions of water = 59,5, which may be expelled by heat. They effloresce by exposure to air.
Bicarbonate of Soda is formed by passing carbonic acid through the solution of the subcarbonate. By evaporation, a crystalline mass is obtained. This salt consists of
- 29,5 soda. - 41,4 carbonic acid.
70,9
Barium.
To obtain this metal, the earth baryta is negatively electrized in contact with mercury; an amalgam is gradually formed, from which the mercury may be expelled by heat, and the metal barium remains, appearing, according to Sir H. Davy, of a dark grey colour, and being more than twice as heavy as water. It greedily absorbs oxygen, and burns with a deep red light when gently heated, producing the oxide of barium.
Oxide of Barium, or baryta, is obtained by exposing the nitrate of baryta to a bright red heat. It is of a grey colour, and very difficult of fusion, and appears to consist of 65 barium + 7,5 oxygen, and Chemistry is consequently represented by 72,5. It eagerly absorbs water, heat is evolved, and a white solid is formed, containing about 10 per cent. of water; this is the hydrate of baryta, and may be considered as a compound of 1 proportion of baryta = 72,5 + 1 proportion of water = 8,5, and is consequently represented by 81.
This hydrate dissolves in boiling water; and, as the solution cools, deposits flattened hexagonal prisms, which contain a large quantity of water.
Baryta, like the alkalies, converts vegetable blues to green, and serves as an intermede between oil and water, whence it has been called an alkaline earth.
It exists in two natural combinations only,—namely, as sulphate and carbonate. According to M. Gay-Lussac, there is a peroxide of barium obtained by heating baryta in oxygen.
Chloride of Barium may be obtained by heating baryta in chlorine, in which case oxygen is evolved; or more easily by dissolving carbonate of baryta in diluted muriatic acid. By evaporation, tabular crystals are obtained, soluble in five parts of water at 60°; and consisting, when dry, of 65 barium + 33,5 chlorine = 98,5.
Chlorate of Baryta is formed in the same way as chlorate of potash. It crystallizes in quadrangular prisms, soluble in four parts of water, at 60°. It consists of
\[ \begin{align*} 1 \text{ proportion of baryta} &= 72,5 \\ 1 \text{ chloric acid} &= 71, \\ &= 143,5 \end{align*} \]
Or of 1 proportion of barium = 65,
\[ \begin{align*} 6 \text{ of oxygen} &= 45, \\ 1 \text{ of chlorine} &= 33,5 \\ &= 143,5 \end{align*} \]
Guy-Lussac procured chloric acid by the action of sulphuric acid upon this salt.
Iodate of Baryta is a very difficultly soluble compound—the hydriodate is crystallizable and very soluble.
Nitrate of Baryta crystallizes in octoedrons; it is soluble in 12 parts of cold and 4 of boiling water; it is decomposed by heat, furnishing pure baryta.
It consists of 72,5 baryta,
\[ \begin{align*} 50,5 \text{ nitric acid}. \end{align*} \]
123.
Sulphuret of Barium and Phosphuret of Barium are brown compounds, which act upon water, as already described, producing hydrosulphuret and hydrophosphuret of baryta.
Sulphate of Baryta is an abundant natural product; it is insoluble, and therefore produced whenever sulphuric acid or a soluble sulphate is added to any soluble salt of baryta. Hence the solutions of baryta are accurate tests of the presence of sulphuric acid. They are all highly poisonous, and sulphate of soda, or dilute sulphuric acid, are the best anti- Chemistry. Sulphate of barytes consists of one proportion of sulphuric acid and one of baryta.
\[ \begin{align*} 37.5 \text{ sul. a.} \\ 72.5 \text{ baryta.} \end{align*} \]
110.
Phosphate of Barytes consists of
\[ \begin{align*} 25 \text{ phosphoric acid.} \\ 72.5 \text{ baryta.} \end{align*} \]
97.5
It is insoluble in water, and therefore formed by adding a solution of phosphoric acid or phosphate of soda to nitrate or muriate of baryta.
Carbonate of Baryta is found native. Artificially produced it is a white compound insoluble in water, containing 20.7 carb. acid.
\[ \begin{align*} 72.5 \text{ baryta.} \end{align*} \]
93.2
Strontium
Is procured from the earth strontia by the same process as barium, which metal it resembles in appearance.
Oxide of Strontium, or the earth Strontia, is procured by the ignition of the pure nitrate; it is of a grey colour; it forms a pulverulent, and a crystallized hydrate. It consists of 44.5 strontium.
\[ \begin{align*} 7.5 \text{ oxygen.} \end{align*} \]
52
The pulverulent hydrate contains 52 strontia.
8.5 water.
60.5
Strontia and its soluble compounds are not poisonous; they tinge the flame of alcohol blood-red, while the corresponding compounds of baryta give it a yellow tint.
Chlorine and Strontium.—This compound, which has also been called Muriate of Strontia, is commonly procured by dissolving carbonate of strontia in muriatic acid. It crystallizes in slender six-sided prisms, soluble in twice their weight of water at 60°. When chlorine is made to act upon strontia, it is absorbed, and oxygen evolved. The resulting compound contains 44.5 strontium.
33.5 chlorine.
78
Nitrate of Strontia crystallizes in octoëdra; it is soluble in its weight of water at 60°. It consists of
\[ \begin{align*} 52 \text{ strontia.} \\ 50.5 \text{ nitric acid.} \end{align*} \]
102.5
Sulphate of Strontia occurs native. It is nearly insoluble, 1 part requiring 4000 of water for its solution. When heated with charcoal, its acid is decomposed, and sulphuret of strontia is formed, which affords nitrate by the action of nitric acid. This process, equally practicable upon sulphate of baryta, is sometimes adopted to obtain the earth. Sulphate of strontia contains 52 strontia.
37.5 acid.
89.5
Phosphate of Strontia is an insoluble white salt, containing
52 strontia.
25 acid.
77
Carbonate of Strontia exists native. Artificially formed, it is a white insoluble body, containing
52 strontia.
20.7 carbonic acid.
72.7
Calcium.
When lime is electrized negatively in contact with mercury, an amalgam is obtained, which, by distillation, affords a white metal. It has been called calcium, and, when exposed to air, and gently heated, it burns, and produces the oxide of calcium, or lime.
Lime appears to consist of 19 parts of this metallic base united to 7.5 parts of oxygen, so that its representative number will be = 26.5. The combinations of lime are very abundant natural products, and of these the native carbonate, which, more or less pure, constitutes the different kinds of marble, chalk, and limestone, and which is also the leading hardening principle of shell, coral, &c., may be considered as the most important.
Pure lime may be obtained by exposing powdered white marble to a white heat. Its colour is grey, it is acrid and caustic, and converts vegetable blues to green; its specific gravity is 2.3, it is very difficult of fusion. Exposed to air it becomes white by the absorption of water and a little carbonic acid. When thrown into water, a considerable rise of temperature ensues. At the temperature of 60°, 750 parts of water are required for the solution of one part of lime.
Chloride of Calcium is produced by heating lime in chlorine; in which case oxygen is evolved; or by evaporating muriate of lime to dryness, and exposing the dry mass to a red heat in close vessels. It consists of 19 calcium + 33.5 chlorine = 52.5. This compound has a strong attraction for water, it deliquesces when exposed to air, and is difficultly crystallizable from its aqueous solutions.
Iodate of Lime is difficultly crystallizable in small quadrangular prisms.
Hydroiodate of Lime is very deliquescent; when dried, it becomes Iode of Calcium, a white fusible compound.
Nitrate of Lime is a deliquescent salt soluble in 4 parts of water at 60°. It is found in old plaster and mortar, from the washings of which nitre is pro- cured by the addition of subcarbonate of potash. It is composed of
| Lime | 26.5 | |------|------| | Nitric acid | 50.5 |
77
Sulphuret of Lime is formed by heating lime with sulphur. It is soluble in water with the same phenomena as sulphuret of potash.
Sulphate of Lime occurs native in selenite, gypsum, and plaster stone. It is easily formed artificially, and then affords silky crystals soluble in 350 parts of water. When these or the native crystallized sulphate are exposed to a red heat, they lose water, and fall into a white powder (plaster of Paris), which, made into a paste with water, soon solidifies. Dry sulphate of lime consists of
| 26.5 lime | 37.5 sulp. acid. | |-----------|-----------------| | | |
64
Crystalline selenite contains two proportions of water, and is consequently represented by 64 + 17, or 81. As sulphate of lime is more soluble in water than pure lime, sulphuric acid affords no precipitate when added to lime-water. Nearly all spring and river water contains this salt, and in those waters which are called hard it is abundant.
Phosphuret of Lime.—By passing phosphorus over red-hot lime, a brown compound is produced, which rapidly decomposes water with the evolution of phosphuretted hydrogen gas. Hydrophosphuret and phosphate of lime are also formed.
Phosphate of Lime exists abundantly in the bones of animals; it is also found in the mineral world. It may be formed artificially, by mixing solutions of phosphate of soda and of lime. It is insipid and insoluble, but dissolves in dilute nitric and muriatic acid without decomposition. It is decomposed by sulphuric acid, and thus the phosphoric acid for the production of phosphorus is usually procured. It consists of
| 26.5 lime | 25 phosphoric acid. | |-----------|-------------------| | | |
51.5
Superphosphate of Lime may be obtained by dissolving the phosphate in phosphoric acid; by evaporation, it affords small crystalline laminae.
Carbonate of Lime is the most abundant compound of this earth. When lime-water is exposed to air, it becomes covered with an insoluble film of carbonate of lime, and hence is an excellent test of the presence of carbonic acid. But excess of carbonic acid redissolves the precipitate, producing a supercarbonate. Carbonate of lime is precipitated by the carbonated alkalies from solutions of muriate and nitrate of lime. Exposed to a red heat the carbonic acid escapes, and quicklime is obtained.
It consists of
| 26.5 lime | 20.7 carbonic acid. | |-----------|--------------------| | | |
47.2
Fluor Spar—Fluate of Lime.—These terms have been applied to a body containing a peculiar principle which has not hitherto been obtained in an insulated state.
It is a principle which probably belongs to the acidifying supporters of combustion, and which in fluor spar is perhaps united to calcium. It appears to be united with hydrogen in the fluoric, or hydrofluoric acid. This supposed base has been called fluorine by Sir H. Davy; and phlore (from φλόρος, destructive), by M. Ampère.
Hydrofluoric acid (hydrophthoric) is procured by distilling a mixture of one part of the purest fluor spar in fine powder with two of sulphuric acid; the distillatory apparatus and receiver should be of lead or silver; the heat required is not considerable; sulphate of lime remains in the retort; and a highly acrid and corrosive liquid passes over, which requires the assistance of ice for its condensation. This acid is colourless, of a very pungent smell, and extremely destructive. If applied to the skin, it instantly kills the part, produces extreme pain, and extensive ulceration. At 80° it becomes gaseous; it has never been frozen; it produces white fumes when exposed to a moist air. This acid acts upon potassium and sodium, and some other metals, with great energy; hydrogen is evolved, and a peculiar compound, probably of the basis of the acid and of the metal, results. These compounds might be called fluorides.
Fluoboric Acid.—This is probably a compound of fluorine with boron. It is gaseous, and may be obtained by heating in a glass retort twelve parts of sulphuric acid with a mixture of one part of fused boric acid, and two of fluate of lime reduced to a very fine powder. The gas must be received over mercury: 100 cubical inches weigh 73.5 grains; so that the specific gravity of fluoboric acid, compared with hydrogen, is 32.68; and, with atmospheric air, 2.371. It produces very copious fumes when suffered to escape into a moist atmosphere; and, when acted upon by water which dissolves 700 times its volume, it affords a solution of hydrofluoric and boracic acids, whence it would seem that the hydrogen is transferred to the fluorine, and the oxygen to the boron. It acts with great energy on vegetable and animal bodies, depriving them of moisture and hydrogen.
Magnesium.
The metallic base of magnesia has not hitherto been obtained; but, when that earth is negatively electrified with mercury, the resulting compound decomposes water, and gives rise to the formation of magnesia.
Magnesia, or Oxide of Magnesium—is concluded, from indirect experiments, to consist of 11 metal + 7.5 oxygen; its representative number, therefore, is 18.5. Magnesia is a white insipid substance, which slightly greens the blue of violets. Its specific gravity is 2.3; it is almost infusible and insoluble in water.
Chloride of Magnesium may be obtained by passing chlorine over red-hot magnesia; oxygen is expelled, and a substance obtained which moisture converts into muriate of magnesia. Chemistry. Muriate of Magnesia is very deliquescent, and difficultly crystallized. Its solution has a bitter saline taste. Exposed to heat, muriatic acid flies off, and the magnesia remains pure. It consists of
Magnesia, 18.5 Muriatic acid, 34.5
Chlorite of Magnesia is a bitter deliquescent salt.
Hydriodate of Magnesia is deliquescent, and loses hydriodic acid by exposure to heat.
Nitrate of Magnesia crystallizes in rhomboidal prisms, deliquescent and soluble in half its weight of water. It contains
Magnesia, 18.5 Nitric acid, 50.5
Sulphate of Magnesia is a commonly occurring compound of this earth, much used in medicine as an aperient. It is largely consumed in the preparation of carbonate of magnesia. It crystallizes in four-sided prisms with reversed dihedral summits, or four-sided pyramids. Its taste is bitter. It is soluble in its own weight of water at 60°. When exposed to a red heat, it loses its water of crystallization, amounting to about 50 per cent., but is not decomposed. It consists of
Magnesia, 18.5 Sulphuric acid, 37.5
In its crystallized state, it may be considered as composed of 1 proportion of dry sulphate + 7 proportions of water;
Or, 56 Sulphate, 59.5 Water.
This salt is usually obtained from sea-water, occasionally from saline springs, and sometimes by the action of sulphuric acid on magnesian limestones.
Carbonate of Magnesia is generally procured by adding carbonated alcalies to a solution of sulphate of magnesia. It is a white, insipid, and insoluble powder, which loses its acid at a red heat, and thus affords pure (calcined) magnesia. It contains
18.5 Magnesia, 20.7 Carbonic acid.
It is soluble in excess of carbonic acid, and this solution affords crystals of bicarbonate, containing
18.5 Magnesia, 41.4 Carbonic acid.
Silicium.
It has been assumed that the earth silica consists of a metallic basis, united with oxygen, and that it contains 50 per cent. of each of its components; so that, if the earth be considered a deutoxide, it will consist of
15 Silicium, 15 Oxygen.
Oxide of Silicium, Silica, or Siliceous Earth—is a very abundant natural product. It exists pure in rock-crystal, and nearly pure in flint. Its colour is white; its specific gravity 2.66. It fuses at a very high temperature. In its ordinary state it is insoluble in water; but it dissolves in very minute portions in that fluid, when recently precipitated in the form of hydrate; and in the same state it dissolves in the acids. It readily unites with the fixed alcalies, and forms glass; or, if the alcali be in excess, a liquid solution of the earth may be obtained, whence it is precipitated in the state of a gelatinous hydrate by acids.
The only body which acts energetically upon silica is the hydrofluoric acid. The result of this action is a gaseous compound, which has been called silicated fluoric acid; it is probably a compound of silicium and fluorine. To obtain this gas, three parts of fluor spar, and one of silica finely powdered, are mixed in a retort with an equal weight of sulphuric acid; a gentle heat is applied, and the gas evolved is to be collected over mercury.
Silicated fluoric acid is a colourless gas; its odour is acrid, much resembling muriatic acid; its taste very sour; its specific gravity 3.574 to air; 100 cubic inches = 110.78 grains, so that its specific gravity to hydrogen is 4.92. It extinguishes burning bodies. It produces white fumes when in contact with damp air, and when exposed to water, a little hydrogen is evolved, and two compounds of silica with fluoric acid are formed; the one acid, and dissolved in the water, the other containing excess of earth, and insoluble. The dry gas contains 62 per cent. of silica; the aqueous solution only retains 55 per cent. Water dissolves 260 times its bulk of this gas. When one volume of silicated fluoric acid is mixed with two of ammonia, a total condensation ensues, and a dry silica fluicate of ammonia results. Potassium, when heated in this gas, burns and produces a brown compound, which, when dissolved in water, affords fluicate of potash. The uses of silica are numerous and important; it forms an ingredient in pottery and porcelain, and with alcali it forms glass. It appears from the experiments of Mr J. F. Daniell, that silicium exists in some of the varieties of cast iron. (Journal of Science and Arts, Vol. II.)
Aluminium.
The earth alumina constitutes some of the hardest gems, such as the sapphire and ruby, and it gives a peculiar softness and plasticity to some earthly compounds, such as the different kinds of clay. It is analogically considered as a metallic oxide. To obtain pure alumina we add carbonate of potash to a solution of alum, and ignite the precipitate; it is a tasteless white substance, forming a cohesive mass with water, and retaining water even at a red heat; its specific gravity is 2; it is soluble in soda and potash; and forms compounds with baryta, strontia, lime, and silica. It is an essential ingredient in pottery and porcelain.
One of its saline combinations is of important use in the arts, namely alum; a triple sulphate of alumina and potash. This salt is usually prepared by roasting and lixiviating certain clays containing pyrites; to the lyes, a certain quantity of potash is added, and the triple salt is obtained by crystallization.
Alum has a sweetish astringent taste. It dissolves in five parts of water at 60°, and the solution reddens blues. It furnishes octoëdral crystals. When heated, it loses water of crystallization, and a part of its acid, and becomes a white spongy mass. In its crystalline form, it consists of
| Substance | Specific Gravity | |---------------|------------------| | Sulphuric acid| 33 | | Alumina | 12 | | Potash | 9 | | Water | 46 |
When alum is ignited with charcoal, a spontaneously inflammable compound results, which has long been known under the name of Homberg's pyrophorus. The potash is decomposed in this process, along with the acid of the alum, and pyrophorus is a compound of sulphur, charcoal, and potassium, with alumina.
Zirconium.
The earth zircon, or the oxide of zirconium, is a white insipid substance; specific gravity 4.8; it is found in the zircon of Ceylon; it is characterized by insolubility in pure alkalies, but is soluble in alkaline carbonates. Its combinations with the acids are of difficult solubility or insoluble, and have been very little inquired into.
Yttrium.
The earth yttria derives its name from Yttertz in Sweden; it is found in the mineral called gadolinite. It is white and tasteless; its specific gravity = 4.84. It is insoluble in the caustic alkalies, but dissolves sparingly in carbonate of ammonia. Its saline combinations have been scarcely examined.
Glaucium.
The earth glaucine was discovered by Vauquelin in the beryl; it also exists in the emerald of Peru; it is white and insipid; its specific gravity = 2.97. It dissolves in caustic potash, and soda, and thus resembles alumine, but differs from yttria. Again, it differs from alumine, but resembles yttria in being soluble in carbonate of ammonia; it is much more soluble in this solution than yttria. With the acids it forms saline compounds of a sweetish astringent taste.
### TABLE
Exhibiting the Specific Gravities and Representative Numbers of the Metals, and of their Combinations; with the General and Distinctive Characters of the Metallic Salts.
| Substances | Specific Gravity | Representative Number | Composition | Remarks | |---------------------|------------------|-----------------------|-------------|---------| | Metals of First Class | | | | | | Gold | 19.80 | 97 | 97 G. + 7.5 ox. | The salts of gold are yellow and soluble in water. Potash and soda produce in them yellow precipitates. Sulphuretted hydrogen and hydrosulphuret of ammonia occasion black precipitates, phosphuretted hydrogen, a purple precipitate, a plate of tin or muriate of tin, a purple powder. Sulphate of iron separates minutely divided metallic gold. Tincture of galls gives a brown precipitate. Triple prussiate of potash occasions no precipitate. | | peroxide | | | | | | chloride | | | | | | muriate | | | | | | chlorate | | | | | | iodide | | | | | | hydriodate | | | | | | nitrate | | | | | | sulphuret | | | | | | sulphite | | | | | | sulphate | | | | | | hydrosulphuret | | | | | | phosphuret | | | | | | phosphite | | | | | | phosphate | | | | | | SUBSTANCES | Specific Gravity | Representative Number | Composition | REMARKS | |------------|-----------------|-----------------------|-------------|---------| | Gold hydrophuret | | | | The salts of silver are reduced upon charcoal by the blowpipe. The soluble salts are precipitated by the alcalies, which furnish dark olive precipitates; by sulphuretted hydrogen and hydrosulphuret of ammonia, nearly black; by infusion of galls, yellow brown; by prussiate of potash and iron, white. Muriatic acid and the muriates give white precipitates of chloride of silver. Sulphate of iron, and a plate of copper, throw down metallic silver. | | carbonate | | | | | | cyanuret | | | | | | prussiate | | | | | | borate | | | | | | Silver | 10.50 | 102 | 109.5 O.S. + 7.5 ox. | A detonating salt. Hydriodic acid throws down iode of silver from the nitrate, at first white, but becoming very soon yellow, then grey and blackish. | | oxide | | | | | | chloride | | | | | | muriate | | | | | | chlorate | | | | | | iodide | | | | | | hydriodate | | | | | | nitrate | | | | | | ammoniuret | | | | | | sulphuret | | | | | | sulphite | | | | | | sulphate | | | | | | hydrosulphuret | | | | | | phosphuret | | | | | | phosphate | | | | | | carbonate | | | | | | cyanuret | | | | | | hydrocyanate | | | | | | borate | | | | | | Platinum | | | | | | protoxide | | | | | | peroxide | | | | | | chloride | | | | | | muriate | | | | | | iodide | | | | | | hydriodate | | | | | | nitrate | | | | | | ammoniuret | | | | | | ammonia muriate | | | | | | sulphuret | | | | | | sulphate | | | | | | hydrosulphuret | | | | | | phosphuret | | | | | | phosphate | | | | | | prussiate | | | | | | Palladium | 11.50 | | | Contains, according to Vauquelin, 20 per cent oxygen. The Salts of Palladium are precipitated by sulphate of iron; also brown by sulphuretted hydrogen; black by muriate of tin; greenish brown by prussiate of potash; deep orange by sulphate and nitrate of potash. The Salts of Rhodium are not... |
The solutions of these salts are deep or brownish yellow. They afford no precipitate with solutions of soda, of sulphate of iron, or of prussiate of potash. The addition of the latter produces a fine green solution. Potash and ammonia, and many of their salts, occasion yellow precipitates. Sulphuretted hydrogen occasions a black precipitate. Infusion of galls gives a dingy precipitate.
Hydrosulphuret of ammonia produces a brown precipitate in muriate of platinum. This is probably a sulphuretted hydrosulphuret.
A soluble salt, obtained by dissolving oxide of platinum in phosphoric acid.
Rhodium | SUBSTANCES | Specific Gravity | Representative Number | Composition | REMARKS | |------------|-----------------|-----------------------|-------------|---------| | Rhodium oxide | | | precipitated by muriate of ammonia, hydrosulphuret of ammonia, prussiate of potash, or alkaline carbonates. The caustic alcalies occasion a yellow precipitate. The salts of iridium are soluble in water, and generally of a blue colour. | | Iridium oxide | | | | | | **Metals of Second Class** | | | | | | Osmium oxide | | | | | | Mercury | 13.50 | 190 | 197.5 M. + 7.5 O. | The Mercurial Salts are volatilized by heat. They are precipitated yellowish by prussiate of potash; deep brown by hydrosulphuret of ammonia; and copper separates pure mercury. The salts, with the protoxide, furnish black precipitates with the alcalies, and white with muriatic acid. The salts with the peroxide furnish to the fixed alcalies reddish precipitates, and white with ammonia. | | protoxide | | | | | | peroxide | | | | | | chloride | | | | | | bichloride | | | | | | muriate | | | | | | chlorate | | | Chlorate of Mercury is yellow and insoluble. Oxychlorate furnishes crystals. | | | iode | | | | | | hydriodate | | | | | | nitrate | | | | | | sulphuret | | | | | | bisulphuret | | | | | | sulphite | | | | | | sulphate | | | | | | oxysulphate | | | | | | superoxysulphate | | | | | | suboxysulphate | | | | | | hydrosulphuret | | | | | | phosphuret | | | | | | phosphate | | | | | | oxyphosphate | | | | | | carbonate | | | | | | cyanuret | | | | | | prussiate | | | | | | Lead | 11.35 | 97 | 205 O. M. + 50 P. A. | Hydriodic Acid furnishes a yellow precipitate in solutions of protoxide, and a red precipitate with the peroxide. These are the protiode and periode of mercury. Phosphoric Acid produces a white insoluble precipitate in nitrate of mercury, but no precipitate in the oxynitrate. | | 1. oxide | | | | | | 2. oxide | | | | | | 3. oxide | | | | | | chloride | | | | | | chlorate | | | A soluble salt, crystallizing in brilliant laminae. | | | iode | | | | | | nitrate | | | | | | sulphuret | | | | | | sulphate | | | | | | hydrosulphuret | | | | | | phosphuret | | | | | | phosphate | | | | | | carbonate | | | | | | prussiate | | | | | | Nickel | 8.25 | 55.5 | 55.5 N. + 15 O. | The Salts of Nickel furnish green solutions, of a sweetish acrid flavour; ammonia furnishes green precipitates, redissoluble in excess of alcali, and forming triple salts. Prussiate of potash forms a greenish precipitate; hydrosulphuret of ammonia gives a black | | oxide | | | | | | hydrate | | | | | | chloride | | | | | | muriate | | | | | | nitrate | | | | | | ammonuret | | | | | | sulphuret | | | | | | supersulphuret | | | | | | SUBSTANCES | Specific Gravity | Representative Number | Composition | REMARKS | |------------------|------------------|-----------------------|----------------------|------------------------------------------------------------------------| | Nickel sulphate | | | 70.5 O. N. + 37.5 S. A. | precipitate; hydriodic acid forms a pea-green iode. | | phosphuret | | | 75.5 N. + 20 P. | | | phosphate | | | 95.5 O. N. + 25 P. A. | | | carbonate | | | 91.2 O. N. + 20.7 C. A.| | | prussiate | | | | |
**Metals of Third Class**
| Arsenic | 8.35 | 45 | | | |------------------|------------------|-----------------------|----------------------|------------------------------------------------------------------------| | 1. oxide | | | 60 | 45 A. + 15 O. | | 2. oxide | | | 67.5 | 45 A. + 22.5 O. | | chloride | | | 112 | 45 A. + 67 C. | | muriate | | | | | | iodide | | | | | | hydruret | | | | | | arsenic hydrogen | | | | | | sulphuret | | | 60 | 45 A. + 15 S. | | bisulphuret | | | 75 | 45 A. + 30 S. | | sulphate | | | | |
**Arsenate of ammonia**
| silver | | | | | | mercury | | | | | | lead | | | | | | nickel | | | | |
**Molybdenum**
| 1. oxide | 7.40 | 44 | 51.5 | 44 M. + 7.5 O. | | 2. oxide | | | 59 | 44 M. + 15 O. | | 3. oxide | | | 66.5 | 44 M. + 22.5 O. | | sulphuret | | | 74 | 44 M. + 30 S. |
**Chrome**
| 1. oxide | | | | | | 2. oxide | | | | |
**Tungsten**
| 1. oxide | | | | | | 2. oxide | | | | |
**Columbium**
Hydriodic Acid produces a precipitate of white oxide of arsenic, when added to arsenite of potash, and hydriodate of potash is formed. Arsenite of potash gives a white precipitate, with hydrosulphuret of ammonia; a white precipitate soon becoming yellow and brown with nitrate of silver; a grey precipitate with nitrate, and a white with oxynitrate of mercury; a white with nitrate of lead; a pale green with nitrate of nickel; pale pink by nitrate of cobalt; apple green with nitrate of copper; white with the muriate and oxymuriate of tin; dingy green with the muriate and oxymuriate of iron; white with sulphate of zinc; bright yellow with nitrate of uranium.
The Arseniate of Potash produces a reddish precipitate in nitrate of silver; straw-coloured with nitrate, and yellow with oxynitrate of mercury; white with nitrate of lead; pale green with nitrate of nickel; pale blue with nitrate of copper; pink with nitrate of cobalt; white with muriate of tin; no precipitate with oxymuriate of tin; pale sea-green with muriate and oxymuriate of iron; straw colour with nitrate of uranium; and white with sulphate of zinc.
The compounds of the arsenic and arsenious acids are decomposed when heated with charcoal, and exhale an alliaceous smell.
Chromic Acid and Chromate of Soda produce insoluble precipitates in solutions of silver, mercury, lead, copper, iron, and uranium; the colours are crimson, red, yellow or orange, apple green, brown, and yellow. No precipitate is formed in solutions of nickel, zinc, tin, cobalt, gold, or platinum. | Substances | Specific Gravity | Representative Number | Composition | Remarks | |------------|-----------------|-----------------------|-------------|---------| | Antimony | | | | | | 1. oxide | 6.70 | 85 | 85 A. + 15 O. | The soluble binary salts of the protoxide of antimony are precipitated white by water; the precipitate is a subsalt. Sulphuretted hydrogen, and hydrosulphuret of ammonia, give an orange precipitate, and a plate of iron or zinc throws down the metal in the form of a black powder. | | 2. oxide | | | | | | chloride | | | | | | muriate | | | | | | iode | | | | | | sulphuret | | | | | | sulphate | | | | | | hydrosulphuret | | | | | | phosphuret | | | | | | phosphate | | | | | | Uranium | 9 | | | Of the Salts of Uranium the greater number are soluble, and of a greenish yellow colour; they form yellow precipitates with the alcalies, and afford a reddish yellow iode with hydriodic acid. Prussiate of potash forms a precipitate of a rich brown colour, and hydrosulphuret of ammonia one nearly black. | | oxide | | | | | | Cerium | | | | Nearly all the Salts of Cobalt are of a red colour; potash, soda, and ammonia, produce in them blue precipitates of hydrated oxide, which is soluble in excess of ammonia, producing a red solution. Hydrosulphuret of ammonia gives a black precipitate. Prussiate of potash a pale green. Carbonates, phosphates, and arseniates, produce red precipitates. Hydriodic acid does not precipitate the salts of cobalt. | | 1. oxide | | | | | | 2. oxide | | | | | | Cobalt | 8 | | | | | 1. oxide | | | | | | 2. oxide | | | | | | chloride | | | | | | muriate | | | | | | sulphuret | | | | | | sulphate | | | | | | hydrosulphuret | | | | | | phosphuret | | | | | | phosphate | | | | | | Titanium | | | | The Salts of Titanium are colourless, and afford white precipitates with the alcalies. Prussiate of potash gives a green precipitate, and infusion of galls a red one. Hydrosulphuret of ammonia gives a green precipitate. | | 1. oxide | 135 | | 135 T. + 7.5 O. | | | 2. oxide | | | | | | 3. oxide | | | 135 T. + 15 O. | | | Bismuth | | | | The Salts of Bismuth are precipitated white by water—brownish black by sulphuretted hydrogen—yellowish white by precipitate of potash, and hydriodic acid affords a deep brown iode of bismuth. | | oxide | 9.80 | 66.5 | 66.5 B. + 7.5 O. | | | chloride | | | | | | nitrate | | | | | | sulphuret | | | | | | sulphate | | | | | | hydrosulphuret | | | | | | Copper | | | | The salts of this metal are distinguished by their blue and green colours; their solutions afford blue precipitates of hydrated oxide with the alcalies, and these redissolve in excess of ammonia, producing a deep blue solution. A plate of iron precipitates metallic copper; prussiate of potash affords a | | 1. oxide | 8.90 | 60 | 60 C. + 7.5 O. | | | 2. oxide | | | | | | 1. chloride| | | | | | 2. chloride| | | | | | submuriate | | | | | | muriate | | | | | | chlorate | | | | | | nitrate | | | | | | ammoniuret | | | | | | SUBSTANCES | Specific Gravity | Representative Number | Composition | REMARKS | |--------------------|------------------|-----------------------|-------------------|------------------------------------------------------------------------| | Copper sulphuret | | | 75 C. + 15 S. | fine brown precipitate; hydrosulphuret of ammonia one of a dirty brown; hydriodic acid produces an insoluble iode of an ash grey colour. | | bisulphuret | | | 90 C. + 30 S. | | | sulphite | | | | | | sulphate (dry) | | | 75 O. C. + 75 S. A.| | | hydrosulphuret | | | | | | phosphuret | | | | | | phosphate | | | 92.5 | | | oxyposphate | | | 125 | | | carbonate | | | 95.7 | | | prussiate | | | | | | Tellurium | | | | | | oxide | | | 6.10 | | | chloride | | | | | | Metals of Fourth Class | | | | | | Iron | | | | | | 1. oxide | | | 7.78 | | | 2. oxide | | | | | | 1. chloride | | | | | | 2. chloride | | | | | | muriate | | | | | | oxymuriate | | | | | | chlorate | | | | | | iodide | | | | | | nitrate | | | | | | oxynitrate | | | | | | sulphuret | | | | | | bisulphuret | | | | | | sulphate | | | | | | crystallized | | | | | | oxysulphate | | | | | | hydrosulphuret | | | | | | phosphuret | | | | | | oxyposphate | | | | | | carburet | | | | | | carbonate | | | | | | prussiate | | | | | | Tin | | | | | | 1. oxide | | | 7.30 | | | 2. oxide | | | | | | 1. chloride | | | | | | 2. chloride | | | | | | muriate | | | | | | oxymuriate | | | | | | iodide | | | | | | nitrate | | | | | | sulphuret | | | | | | bisulphuret | | | | | | sulphate | | | | | | hydrosulphuret | | | | | | phosphuret | | | | | | prussiate | | | | | | Zinc | | | | | | oxide | | | 7 | | | chloride | | | | | | muriate | | | | | | iodide | | | | | | hydriodate | | | | | | nitrate | | | | |
The Solutions of Iron are known by affording a purple or black precipitate to infusion of galls. They give no precipitate with hydriodic acid.
The Hydriodic Acid affords a fine orange precipitate with solution of muriates of tin, provided there be no excess of acid. Hydrosulphuret of ammonia produces a precipitate of a deep orange colour. The other characters are noticed in the text.
The Solutions of Zinc are not precipitated by hydriodic acid. Potash, soda, and ammonia form white precipitates redissoluble in excess either of acid or alkali. Hydrosulphuret of ammonia produces a | SUBSTANCES | Specific Gravity | Representative Number | Composition | REMARKS | |------------|-----------------|-----------------------|-------------|---------| | Zinc sulphuret | 48 | 33 Z. + 15 S. | yellowish white precipitate, and the soluble phosphates, borates, and carbonates, all form white precipitates. | | sulphate | 78 | 40.5 O. Z. + 37.5 S. A. | | | hydrosulphuret | | | | | phosphate | 65.5 | 40.5 O. Z. + 25 P. A. | | | carbonate | 61.2 | 40.5 O. Z. + 20.7 C. A. | | | prussiate | | | | | Manganese | 6.85 | 56.5 | The Salts of Manganese are not precipitated by hydriodic acid. They furnish white precipitates with the alkalies, which blacken by exposure to air. They are precipitated white by prussiate of potash, and yellow by hydrosulphuret of ammonia. | | 1. oxide | | 71.5 | 56.5 M. + 15 O. | | hydrate | | 88.5 | 71.5 O. M. + 17 W. | | 2. oxide | | 79 | 56.5 M. + 22.5 O. | | chloride | | 123.5 | 56.5 M. + 67 C. | | muriate | | 140.5 | 71.5 O. M. + 69 M. A. | | nitrate | | 146.5 | 71.5 O. M. + 75 S. A. | | sulphuret | | 112.9 | 71.5 O. M. + 41.4 C. A. | | sulphate | | | | | phosphate | | | | | carbonate | | | | | prussiate | | | |
**Metals of Fifth Class**
| Potassium | 0.85 | 37.5 | The following characters belong to the Salts of Potassium: They are all soluble in water, and afford no precipitates with pure or carbonated alkalies; they produce a precipitate in muriate of platinum, which is a triple compound of potassic oxide of platinum, and muriatic acid. They are not changed by sulphuretted hydrogen, nor by prussiate of potash. Added to sulphate of alumine, they enable it to crystallize so as to form alum. | | protoxide | | 45 | 37.5 P. + 7.5 O. | | hydrate | | 53.5 | 45 O. P. + 8.5 water. | | peroxide | | 60 | 37.5 P. + 22.5 O. | | chloride | | 71 | 37.5 P. + 33.5 C. | | chlorate | | 116 | 45 O. P. + 71 C. A. | | iodide | | 155.25 | 37.5 P. + 117.75 I. | | hydriodate | | 163.75 | 45 O. P. + 118.75 H. A. | | oxidate | | | | | hydruret | | | | | hyd. potassuretted | | | | | nitrate | | 95.5 | 45 O. P. + 50.5 N. A. | | sulphuret | | 52.5 | 37.5 P. + 15 S. | | sulphite | | 75 | 45 O. P. + 30 S. A. | | sulphate | | 82.5 | 45 P. + 37.5 S. A. | | bisulphate | | 120 | 45 O. P. + 75 S. A. | | phosphuret | | | | | phosphite | | 62.5 | 45 O. P. + 17.5 P. A. | | phosphate | | 70 | 45 O. P. + 25 P. A. | | carbonate | | 65.7 | 45 O. P. + 20.7 C. A. | | bicarbonate | | 86.4 | 45 O. P. + 41.4 C. A. | | cyanuret | | | | | prussiate | | | | | arsenite | | | | | arseniate | | | | | chromate | | | |
| Sodium | 0.9 | 22 | All the Salts of Soda are soluble in water; they are not precipitated by pure or carbonated alkalies, nor by hydrosulphuret of ammonia, nor prussiate of potash; nor do they produce any precipitate in solution of muriate of platinum. They do not convert sulphate of alumine into alum. | | 1. oxide | | 29.5 | 22 S. + 7.5 O. | | hydrated | | 38 | 29.5 O. S. + 8.5 W. | | peroxide | | 55.5 | 22 S. + 33.5 C. | | chloride | | 100.5 | 29.5 O. S. + 71 C. A. | | chlorate | | 139.75 | 22 S. + 117.75 I. | | iodide | | 184.75 | 29.5 O. S. + 155.25 O. A. | | oxiodate | | 148.25 | 29.5 O. S. + 118.75 H. A. | | hydriodate | | 80 | 29.5 O. S. + 50.5 N. A. | | nitrate | | | | | sulphuret | | | | | sulphite | | | | | Substances | Specific Gravity | Representative Number | Composition | Remarks | |------------------|------------------|-----------------------|----------------------|------------------------------------------------------------------------| | Sodium | | | | | | sulphate | 67 | | 29.5 O.S. + 37.5 S.A. | | | phosphuret | | | 29.5 O.S. + 17.5 P.A. | | | phosphite | 47 | | 29.5 O.S. + 25 P.A. | | | phosphate | 54.5 | | 29.5 O.S. + 50 P.A. | | | biphosphate | 79.5 | | 29.5 O.S. + 20.7 C.A. | | | subcarbonate | 50.2 | | 29.5 O.S. + 41.4 C.A. | | | bicarbonate | 70.9 | | | | | cyanuret | | | | | | prussiate | | | | | | subborate | | | | | | arseniate | | | | | | Barium | | | | | | oxide | 65 | | 65 B. + 7.5 O. | The Soluble Barytic Salts furnish white precipitates of carbonate of bar- | | | | | yta, by the alkaline subcarbonates. Sulphuric acid and the soluble sul- | | | | | phates occasion white precipitates of sulphate of barita in the solution | | | | | of the earth. They are poisonous, and tinge flame yellow. | | hydrate | 72.5 | | | | | chloride | 81 | | 72.5 O.B. + 8.5 W. | | | chlorate | 98.5 | | 65 B. + 33.5 C. | | | iodide | 143.5 | | 72.5 O.B. + 71 C.A. | | | oxiodate | | | | | | hyriodate | | | | | | nitrate | 123 | | 72.5 O.B. + 50.5 N.A. | | | sulphuret | | | | | | sulphite | 102.5 | | 72.5 O.B. + 30 S.A. | | | sulphate | 110 | | 72.5 O.B. + 37.5 S.A. | | | phosphuret | | | | | | phosphite | | | | | | phosphate | 97.5 | | 72.5 O.B. + 25 P.A. | | | carbonate | 93.2 | | 72.5 O.B. + 20.7 C.A. | | | Strontium | | | | | | oxide | 44.5 | | 44.5 S. + 7.5 O. | The Salts of Strontium furnish white precipitates with the alkaline sub- | | | | | carbonates, and with sulphuric acid and sulphates; they tinge flame of | | | | | a fine red; they are not poisonous. They are decomposed by barita, which | | | | | has a stronger attraction for acids than strontia; they are more soluble | | | | | than barytic salts, but pure strontia is less soluble than barita. | | hydrate | 52 | | | | | chloride | 60.6 | | 52 O.S. + 8.5 W. | | | muriate | 78 | | 44.5 S. + 33.5 C. | | | nitrate | 86.5 | | 52 O.S. + 34.5 M.A. | | | sulphuret | 102.5 | | 52 O.S. + 50.5 N.A. | | | sulphate | | | | | | phosphate | 89.5 | | 52 O.S. + 37.5 S.A. | | | carbonate | 77 | | 52 O.S. + 25 P.A. | | | Calcium | | | | | | oxide | 19 | | 19 C. + 7.5 O. | The Salts of Lime furnish precipitates of carbonate of lime by the carbonated | | | | | alcalies; they afford no precipitate with caustic ammonia. Oxalic acid, | | | | | and oxalate of ammonia, produce precipitates of oxalate of lime, which, | | | | | at a red heat, affords quicklime. | | hydrate | 26.5 | | | | | chloride | 35 | | 26.5 O.C. + 8.5 W. | | | muriate | 52.5 | | 19 C. + 33.5 C. | | | chlorate | 61 | | 26.5 O.C. + 34.5 M.A. | | | iodide | 97.5 | | 26.5 O.C. + 71 C.A. | | | oxiodate | 136.7 | | 19 C. + 117.7 I. | | | hyriodate | 181.75 | | 26.5 O.C. + 155.25 O.A.| | | nitrate | 145.2 | | 26.5 O.C. + 118.7 H.A.| | | sulphate | 77 | | 26.5 O.C. + 50.5 N.A. | | | sulphuret | 64 | | 26.5 O.C. + 37.5 S.A. | | | phosphuret | | | | | | phosphate | 51.5 | | 26.5 O.C. + 25 P.A. | | | biphosphate | 76.5 | | 26.5 O.C. + 50 P.A. | | | carbonate | 47.2 | | 26.5 O.C. + 20.7 C.A. | | | fluoride | | | | | | Hydrofluoric acid| | | | | | Fluoboric gas | 32.68 | tohydrog. | | | | Metals of Sixth Class | | | | | | Magnesium | | | | | | oxide | 11 | | 11 M. + 7.5 O. | The salts of magnesia are decomposed by solution of pot- ### PART IV.
#### VEGETABLE CHEMISTRY.
This part of the science relates to the chemical changes which are observed during the germination and growth of plants; to the composition of vegetable substances; and to the phenomena and products of fermentation.
The seeds of plants consist of three distinct parts.
1. The exterior coat or membrane. 2. The cotyledons, which form the bulk of the seed. 3. The germ.
When a seed is placed under favourable circumstances for germination, the exterior coat bursts from the swelling of the cotyledons—the germ increases in size—it puts forth a radicle, which soon becomes a perfect root, and a plumula which forms the stem and leaves.
A due temperature, generally between 50° and 70°, a proper supply of moisture and access of air, are the essential requisites for perfect germination.
The oxygen of the atmosphere abstracts carbon from the principles of the cotyledons, by which saccharine matter is formed; this is absorbed by the vessels which, arising from the young germ, ramify through them, and tends to nourish the young plant until its roots are fit for their functions. Water is obviously required in these changes, which terminate in producing a plant with a root, stem, and leaves.
The leaves of plants, when exposed to the sun’s rays, absorb carbonic acid from the atmosphere, and evolve oxygen. If healthy leaves, gathered on a warm dry day, be placed under a jar of air, it will be found that, during the night, those which are thick and fleshy absorb a portion of oxygen, while those which are thin and delicate absorb also oxygen, and evolve a portion of carbonic acid; which, upon exposure to the sun, they again decompose and restore the oxygen: So that thick leaves diminish the bulk of the air to which they are exposed during the night, and increase it in the day. M. de Saussure found the leaves of the *Cactus opuntia* especially adapted for these experiments. It is only the green parts of plants that exhibit these properties. The roots, wood, and flowers, simply evolve a small portion of carbonic acid. From manures and the soil plants absorb small quantities of saline and carbonaceous matter. The salts most commonly found in vegetables are carbonate, sulphate, and phosphate of potash, carbonate and phosphate of lime, phosphate of magnesia. We also find the chlorides of potassium and sodium, the oxides of iron and manganese, and silica.
Vegetable substances may be considered as consisting of **ultimate** and **proximate principles**. Of the **ultimate principles** the most important are Oxygen, Hydrogen, Carbon, and Nitrogen. The three first exist in all vegetable bodies—the latter is confined to a few. To exhibit these elements, a vegetable substance, starch for instance, may be put into a small earthen retort, to which an earthen tube is attached, passing through a furnace, and slightly inclined. To the other extremity of this tube is annexed a receiver, whence a bent glass tube issues to convey the gaseous products to the mercurial trough. The earthen tube is heated to redness, and afterwards the retort is gradually raised to the same temperature—the starch is thus decomposed, and affords charcoal and water, carbonic oxide and acid, and carburetted hydrogen. Sometimes a little empyreumatic oil and acetic acid are formed, and if the vegetable contain nitrogen, there is more or less ammonia produced.
The **proximate principles** of vegetables may be arranged under four divisions, founded upon the nature and proportions of their ultimate components. In the first division are comprised those in which the relative proportion of the oxygen to the hydrogen is greater than in water. In the second, those in which the relative proportions of oxygen to hydrogen are the same as in water; in the third, those in which... Chemistry. there is excess of hydrogen; in the fourth, those which contain nitrogen.
The bodies contained in the first division are all acid, and as they are described in the Article Chemistry of the Encyclopaedia, it will here only be required to enumerate them.
1. Acetic acid, composed of
| Carbon | 50,224 | | Oxygen and hydrogen in the proportions of water | 46,911 | | Excess of oxygen | 2,865 |
Total: 100,000
2. Oxalic Acid, containing
| Carbon | 26,566 | | Oxygen and hydrogen in the proportions of water | 22,872 | | Excess of oxygen | 50,562 |
Total: 100,000
3. Citric Acid, containing
| Carbon | 33,811 | | Oxygen and hydrogen as in water | 52,749 | | Excess of oxygen | 13,440 |
Total: 100,000
4. Tartaric Acid, consisting of
| Carbon | 24,050 | | Oxygen and hydrogen as in water | 55,240 | | Excess of oxygen | 20,710 |
Total: 100,000
5. Benzoic Acid. 6. Camphoric Acid. 7. Gallic Acid. 8. Malic Acid. 9. Suberic Acid.
To these the following have been lately added:
10. Succinic Acid. 11. Mellitic Acid. 12. Saccharic Acid.
Discovered in certain fungi by M. Braconnot. It is deliquescent, uncrystallizable, colourless, and of a very sharp flavour. It forms with baryta a difficultly crystallizable salt, soluble in 15 parts of water at 60°; with potash and soda, uncrystallizable deliquescent salts, insoluble in alcohol; with oxide of zinc a crystallizable salt. Added to acetate of lead it produces a white flocculent precipitate, soluble in distilled vinegar. (See Annales de Chimie, tom. 87.)
14. Kinic Acid, found in combination with lime in cinchona bark. (Vauquelin, Annales de Chimie, tom. 59.)
The law of definite proportions, as applied to salts of vegetable acids, has not been sufficiently investigated.
The substances of the second division contain oxygen and hydrogen, in the same relative proportions as in water. All these bodies are solid, heavier than water, inodorous, and without action on vegetable colours. Their properties are described in the Encyclopaedia (Art. Chemistry). They are,
1. Sugar. 2. Gum. 3. Starch. Iodine is an excellent test for starch. It produces a deep blue colour when added to its solutions. 4. Lignin.* 5. Tannin. (See Mr Hatchett's papers on this subject, Phil. Trans. 1805.) 6. Extractive.
The third division contains bodies with excess of hydrogen; they generally abound in carbon, and are insoluble, or sparingly soluble in water. They are,
1. Fixed Oil. 2. Volatile Oil. 3. Resin. 4. Caoutchouc. 5. Camphor. 6. Wax.†
The fourth division contains one substance only, namely Gluten; which, when submitted to destructive distillation, affords products analogous to those of animal matter, and especially characterized by ammonia.
Besides the bodies which are comprehended in
* MM. Gay-Lussac and Thenard have concluded, from their experiments on the wood of the oak and the beech, that 100 parts of the first contains:
| Of carbon, | 52,53 | | --- | --- | | Oxygen, | 41,78 | | Hydrogen, | 5,69 |
† From the experiments of Gay-Lussac and Thenard, it appears that olive oil contains, in 100 parts,
| Carbon, | 77,213 | | Oxygen, | 9,427 | | Hydrogen, | 13,360 |
Or of Carbon,
| Carbon, | 75,944 | | Oxygen and hydrogen in the proportions necessary to form water, | 15,156 | | Hydrogen in excess, | 8,900 |
According to the same chemists, 100 parts of copal consist of
| Carbon, | 76,811 | | Oxygen, | 10,606 | | Hydrogen, | 12,583 |
100 parts of wax consist of
| Carbon, | 81,784 | | Oxygen, | 5,544 | | Hydrogen, | 12,672 |
Or otherwise,
| Carbon, | 76,811 | | Water or its elements, | 12,052 | | Hydrogen, | 11,197 |
| Oxygen and hydrogen in the proportions necessary to form water, | 6,300 | | Hydrogen, | 11,916 |
| Of carbon, | 51,45 | | --- | --- | | Oxygen, | 42,73 | | Hydrogen, | 5,82 |
| Carbon, | 75,944 | | Oxygen, | 13,337 | | Hydrogen, | 10,719 |
| Carbon, | 76,811 | | Water or its elements, | 12,052 | | Hydrogen, | 11,197 |
| Oxygen and hydrogen in the proportions necessary to form water, | 6,300 | | Hydrogen, | 11,916 |
| Carbon, | 81,784 | | Oxygen, | 5,544 | | Hydrogen, | 12,672 |
| Oxygen and hydrogen in the proportions necessary to form water, | 6,300 | | Hydrogen, | 11,916 | Chemistry. the preceding divisions, there are several other proximate principles of vegetables, the nature of which has not been sufficiently investigated, so as to enable us to class them according to their ultimate components; such as the narcotic principle of opium (Annales de Chimie, 1817), and the colouring matter.
Several different colouring principles have already been recognised, of which the principal are, 1. Hematine, the colouring matter of logwood, soluble in alcohol and in water. 2. Carthamin, from the flowers of the Carthamus tinctorius, insoluble in water and alcohol, but soluble in alcalies. 3. Indigo, insoluble in its ordinary state in water, alcohol, and alcalies, but soluble in sulphuric acid. By the action of certain substances which absorb oxygen, indigo becomes green, and, in that deoxygenized state, is soluble in alcalies. M. Chevreul obtained from 100 parts of indigo of Guatemala the following results: (Annales de Chimie, Tom. 76, p. 29.)
| Dissolved by water | Green matter united to ammonia, a little deoxygenized indigo, gum and extractive. | |--------------------|----------------------------------------------------------------------------------| | Dissolved by alcohol | Green matter, red resin, and a little indigo. | | Dissolved by muriatic acid | Red resin, Carbonate of lime, Red oxide of iron, Alumine. | | Residue | Silica, Pure indigo. |
When indigo is heated, it sublimes in the form of a violet-coloured vapour, much resembling iodine, and condenses in crystals upon the cooler part of the vessels.
**Phenomena and Products of Fermentation.**
Under the articles Chemistry, Brewing, Malt-ting, and Vinegar-making, in the Encyclopaedia, will be found the leading technical and theoretical observations upon the subject of fermentation. The result of this process is the conversion of a portion or the whole of the sugar contained in the original liquor into alcohol. Different wines contain different portions of alcohol, according to the circumstances under which they have been made, and the composition of the juice of the grape or other materials employed. To ascertain the quantity of alcohol which any wine contains, its acid may be saturated with potash; a given measure is then to be distilled with a gentle heat, nearly to dryness, and the deficient bulk of the distilled liquor is to be made up with distilled water. This mixture is to be shaken and set aside for twenty-four hours. Its specific gravity will then show the quantity of alcohol which the wine contains, and which may be immediately seen by reference to Mr Gilpin's tables, published in the Phil. Trans. for 1794. The following table, taken from Mr Brande's paper in the Phil. Trans. for 1811, shows the relative quantity of alcohol contained in the principal wines, &c.
| Wine | Proportion of Alcohol, per cent. by Measure | |-----------------------|---------------------------------------------| | Port | 21.40 | | Ditto | 22.36 | | Ditto | 23.39 | | Ditto | 23.71 | | Ditto | 24.29 | | Ditto | 25.83 | | Madeira | 19.33 | | Ditto | 21.40 | | Ditto | 23.93 | | Ditto | 24.42 | | Sherry | 13.25 | | Ditto | 18.79 | | Ditto | 19.81 | | Ditto | 19.83 | | Claret | 12.91 | | Ditto | 14.08 | | Ditto | 16.32 | | Calcavella | 18.10 | | Lisbon | 18.94 | | Malaga | 17.26 | | Bucellas | 18.49 | | Red Madeira | 18.40 | | Malmsey Madeira | 16.40 | | Marsala | 25.87 | | Ditto | 17.26 | | Red Champagne | 11.30 | | White Champagne | 12.89 | | Burgundy | 14.53 | | Ditto | 11.95 |
The most recent analysis of alcohol is by Mr Th. de Saussure (Annales de Chimie, t. 89), from whose researches it appears, that 100 parts, specific gravity 792, consist of:
- Carbon, 51.98 - Oxygen, 34.32 - Hydrogen, 13.70
It is probable that pure alcohol, free from water, consists of:
100 parts elements of olefiant gas. 50 ———— of water.
**Ethers** are formed by the action of certain acids upon alcohol. The distillation of equal weights of sulphuric acid and alcohol produces sulphuric ether, of which 100 parts, specific gravity 0.7155 at 68°, contain:
- Carbon, 67.98 - Oxygen, 17.62 - Hydrogen, 14.40
Or deprived of adherent water, it may be considered as containing:
100 parts elements of olefiant gas. 25 ———— of water. Chemistry. So that the action of the sulphuric acid in converting alcohol into ether, consists in the removal of one-half of the elements of water which it contains, the proportion of the elements of olefiant gas remaining the same. If the whole of the elements of water be removed from alcohol, olefiant gas is the only result.
Nitric Ether is formed by gradually adding half a pound of nitric acid to two pints of alcohol contained in a glass retort. A pint and a half is to be distilled over by a very gentle heat, which, by redistillation with pure potash, affords nearly a pint of nitric ether. It is heavier than alcohol, and of a peculiar acrid flavour and fragrancy. Passed through a red-hot tube it affords water, prussic acid, ammonia, oil, charcoal, carbonic acid and oxide, carburetted hydrogen and nitrogen, and its oxides.
When equal parts of nitric acid and alcohol are mixed, a violent action soon ensues, and a copious evolution of nitrous etherised gas is the result.
If 100 parts of mercury, dissolved in a measured ounce and a half of nitric acid, be added to two measured ounces of alcohol, and a gentle heat applied, a violent action ensues, during which a whitish powder, which is fulminating mercury, is deposited. It was discovered by Mr Howard, according to whom it consists of oxalate of mercury combined with nitrous etherised gas. Berthollet considers it as containing ammonia, oxide of mercury, and a peculiar vegetable body.
Hydriodic Ether has been obtained by M. Gay-Lussac by distilling a mixture of alcohol and hydriodic acid. (Vide Annales de Chimie, t. 91.)
For an account of the remaining Ethers, and some other vegetable products not noticed here, the reader is referred to the article Chemistry in the Encyclopaedia.
PART V. Animal Chemistry.
The decomposition of animal substances is in general attended by more complicated results than those of vegetables. Ammonia is produced in abundance by the greater number of them, and certain combinations of sulphur and phosphorus with the compounds of carbon, &c., as afforded by vegetable decomposition. Oxygen, hydrogen, carbon, nitrogen, sulphur, and phosphorus, may be considered as the most frequently occurring ultimate elements of animal substances, and these give rise to various compounds produced by their destructive distillation, such as water, subcarbonate of ammonia, prussic acid, &c. &c. Animal substances are decomposed with peculiar phenomena by the acids. Sulphuric acid carbonizes them, and produces water, ammonia, and oily matter; and if heat be applied, the acid is decomposed, and sulphurous gas disengaged. The action of nitric acid is attended by yet more complicated results; it gives rise to the formation of water, carbonic acid, nitrogen, nitrous oxide, nitrous, prussic, acetous, malic, and oxalic acids, ammonia, and a peculiar yellow detonating compound.
Heated with liquid fixed alcalies, animal substances afford ammonia, carbonic and acetic acids, and a peculiar body which forms a soapy compound; and in general, when ignited with potash or soda, cyanurets are formed, which, by the action of water, produce hydrocyanates (prussiates).
The proximate principles of animals have not yet been sufficiently investigated to enable us to arrange them according to their composition; they will be most conveniently examined as resulting from the chemical examination of the different products of animal bodies; these may be considered in the following order:
1. Blood. 2. Bile. 3. Milk. 4. Lymph. 5. Urine. 6. Cutis or skin. 7. Muscles, membranes, ligaments, horn, hair, &c. 8. Oil and fat. 9. Brain and nerves. 10. Shell and bone. 11. Concretions.
Blood.
This fluid, in the large arterial vessels of the more perfect animals, is florid red, and of a brownish red in the veins. Its specific gravity varies from 1083 to 1126. Its temperature is between 97° and 102°. When drawn from the circulating vessels, it undergoes a spontaneous change—forming a firm coagulum and a fluid serum. During this coagulation, there appears to be no increase of the temperature of the blood. (See Dr Davy's Experiments. Journal of Science and Arts, Vol. II. p. 247.)
Serum is a yellow fluid, of a specific gravity of 1029. At a temperature of 160° it coagulates into a firm whitish mass. Serum is also coagulated by alcohol, by most of the acids, and by the negative surface of the Voltaiac pile. The substance in the serum which thus coagulates is called Albumen, a frequently occurring proximate principle of animals, and which exists in considerable purity in the white of egg.
Liquid Albumen is always slightly alkaline; it is soluble in water, and the solution furnishes a flocculent precipitate with corrosive sublimate, and muriate of tin; if not very dilute, it is also precipitated by the other coagulants of albumen. It soon putrefies at the temperature of 60°, and sulphuretted hydrogen is evolved. If dried by a heat between 100° and 120°, it forms a brittle transparent substance like amber.
Coagulated Albumen is insoluble in water; it does not putrify, but, exposed to dry warm air, it gradually becomes tough and semitransparent, and much resembles horn. When digested in water, it affords a weak alkaline solution of albumen. Submitted to destructive distillation, it affords products marked by abundance of ammonia, and a coal remains, very difficult of incineration. (See Mr Hatchett's Papers in the Phil. Trans. for 1799 and 1800.) Dr Marcet obtained the following results from the analysis of 1000 parts of the serum of human blood. (See Medico-Chirurgical Trans. Vol. II.)
| Substance | Parts | |----------------------------|-------| | Water | 900.00| | Albumen | 86.80 | | Muriate of potash and soda | 6.60 | | Muco-extractive matter | 4.00 | | Subcarbonate of soda | 1.65 | When serum or white of egg is coagulated by heat, there oozes from it a yellow fluid, which has been called *serosity*, and which consists of albumen, soda, and water. By washing the coagulum, almost the whole of the alkali may be separated; the acids, alcohol, and negatively electrified surfaces, also separate soda when they coagulate albumen. It appears, then, liquid albumen is a compound of soda and albumen with water; but that, after coagulation, the soda is found with the water, and the albumen solid and with scarcely any alkali.
The Coagulum or Crassamentum of Blood may be separated into two portions by copious washings with water; namely, into a white tough substance having all the essential characters of coagulated albumen, and which has been called *fibrine*, and into colouring matter.
The colouring matter diffused through the serum appears as a number of red globules, which in water part with their colour, and become white, and nearly transparent. In this state they appear to consist of albumen. The red substance is soluble in water, in muriatic, dilute sulphuric, acetic, tartaric, oxalic, and citric acids; the solutions are red by reflected, and green by transmitted light. Alcalies also form red solutions of the colouring principle. Nitric acid instantly destroys it.
Hence it appears that the blood consists of water, albumen, colouring matter, subcarbonate of soda, and certain saline substances, of which common salt is the principal. The cause of its spontaneous coagulation is unknown; the effect which we observe is the solidification of one part of the albumen with the colouring globules, forming the crassamentum; while another portion of the albumen remains fluid, constituting the serum.
**Bile**
Is a bitter greenish-yellow viscid liquid, secreted from venous blood in the liver; its specific gravity fluctuates between 1020 to 1030. The bile of the ox has been principally examined. It is alkaline. It soon putrefies, exhaling an insupportable stench. It dissolves in water, and is only imperfectly coagulated by alcohol, and by acids.
According to the analysis of Thenard (*Traité de Chimie*, p. 556, Vol. III.) bile consists of:
| Substance | Percentage | |----------------------------|-----------| | Water | 700 | | Resinous matter | 15 | | Picromel | 69 | | Yellow matter | 4 | | Soda | 4 | | Phosphate of soda | 2 | | Muriates of soda and potash| 3.5 | | Sulphate of soda | 0.8 | | Phosphate of lime and magnesia | 1.2 | | Traces of oxide of iron | |
Picromel is a principle peculiar to bile, of an acrid bitter and sweet taste, viscid consistency, and which forms a peculiar triple compound with the resin and soda. It is the substance which gives bile its leading characters. It may be obtained by adding to bile an excess of acetate of lead; it is then filtered, and subacetate of lead is added to the filtered liquor, a flocculent precipitate is formed, which is to be washed, and dissolved in distilled vinegar; a current of sulphuretted hydrogen passed through this solution separates the lead; the vinegar is then driven off by heat, and picromel remains.
The yellow matter is also peculiar to bile, and seems to render it easily putrescible.
**Milk**
The gastric secretion of animals coagulates milk, and the cream having been separated, converts it into curd and whey.*
The curd or caseous part of milk (of the cow) is to be considered as a modification of albumen. The whey, by evaporation, affords sugar of milk, a white crystallizable substance, of a sweet taste, composed, according to Guy-Lussac and Thenard, of
| Element | Percentage | |-----------|------------| | Carbon | 38.825 | | Oxygen | 53.834 | | Hydrogen | 7.341 |
or of
| Element | Percentage | |-----------|------------| | Carbon | 38.825 | | Oxygen | 53.834 | | Hydrogen | 7.341 | | Oxygen and hydrogen in the proportions of water | 61.175 |
Butter, according to Braconnot, consists of 60 parts of yellow oil remaining fluid at low temperatures, and 40 parts of concrete oil.
**Lymph**
This fluid, which lubricates the various cavities of the body, and which may be collected in considerable quantities, by puncturing the lymphatic vessels in large animals, has the properties of a weak solution of albumen; it contains the same salts as the serum of blood. The liquor of dropsies is also analogous in composition, but the proportion of albumen varies according to the circumstances under which it has been thrown out. In a case of hydrocele, which had been a long time forming, the liquor afforded a very small proportion (about 3 per cent.) of albumen. The sac filled in five days after the operation, and the fluid then contained 12 per cent. of albumen, and was readily coagulable by the usual means.
**Urine**
This secretion is constantly varying in composition. It is when healthy always acid, but in cases of injury done to the nerves of the kidneys, it is alkaline. The following are the substances contained in human urine.
| Substance | Uncombined, and giving acidity to the urine | |----------------------------|---------------------------------------------| | Water | | | Carbonic acid | | | Uric acid | | | Phosphoric acid | |
* See Sir Everard Home on the Coagulating Power of the Secretion of the Gastric Glands, Phil. Trans. 1813. p. 96. Muriate of soda. Phosphate of soda. Phosphate of ammonia and magnesia. Phosphate of lime. Muriate of ammonia. Sulphates of potash and soda. Urea. Albumen. Gelly.
Occasional ingredients.
Uric acid is occasionally deposited by urine in small red crystals; these are soluble in caustic alcalies, and the uric acid is precipitated from such solutions by muriatic acid. Boiling water dissolves about $\frac{1}{100}$ of its weight of this acid. It is readily soluble in warm nitric acid, and the solution yields by evaporation a rose red compound, very characteristic of this acid.
Urez is the principle which gives to urine its leading peculiarity, that of affording abundance of ammonia during its putrefaction or decomposition by heat. It may be obtained by evaporating urine, voided about six hours after a meal, to the consistence of syrup: to which is to be added four times its weight of alcohol, and a gentle heat applied; the alcoholic solution, by evaporation in a water-bath, affords a crystalline residue of urea. This substance has an acrid taste, and urinous smell; it is soluble in water and alcohol; it forms with nitric acid a compound having the appearance of pearly scales. By heat, it affords two-thirds its weight of subcarbonate of ammonia, and a considerable portion of benzoic acid. Ammonia and acetic acid are the products of the decomposition of its aqueous solution: hence the production of various ammoniacal salts in putrid urine. Alcalies decompose urea, and exhale ammonia. It consists, according to Vauquelin and Fourcroy, of
| Nitrogen | 32.5 | | Oxygen | 28.5 | | Carbon | 14.7 | | Hydrogen | 11.8 |
Cutis.
The cutis, or true skin of animals, consists principally of gelatine, a substance soluble in water, and forming a solution, which, if concentrated while hot, gelatinises on cooling. The solution affords a copious precipitate with vegetable astringents, and with nitrate of mercury it deposits white flocculi with solution of chlorine. Gelatine is soluble both in acids and alcalies. It is insoluble in alcohol, which precipitates it from its aqueous solution. Isinglass, size, and glue, are varieties of gelatine. It contains, according to Thenard and Gay-Lussac,
| Carbon | 47.881 | | Oxygen | 27.207 | | Hydrogen | 7.914 | | Nitrogen | 16.998 |
When submitted to destructive distillation, it affords the usual products of animal bodies. When dry, it suffers no change by exposure to air, but its solution very soon putrefies.*
Muscular Flesh, &c.
When the muscular parts of animals are washed repeatedly in cold water, the fibrous matter which remains consists chiefly of albumen, and is in its chemical properties analogous to the clot of blood. Muscles also yield a portion of gelatine, and the flesh of beef, and some other parts of animals, afford a peculiar substance of an aromatic flavour, called by Thenard osmazome. Ligaments, horn, nail, feathers, and the cuticle, consist principally of albumen. Elastic ligament and tendon yield a portion of gelly. The membranes consist principally of gelatine.
Hair consists principally of a substance, having the properties of coagulated albumen. It also contains gelatine, and the soft kinds of hair yield it more readily than those which are harsh, strong, and elastic.
Vauquelin discovered in hair two kinds of oil; the one white, and existing in all hair, the other coloured, yellow from red hair, and dark coloured when obtained from dark hair. Black hair also contains iron and sulphur. He supposes that where hair has become suddenly grey, the effect is produced by the evolution of acid matter, which has destroyed the colour of the oil.
Oil and Fat.
These proximate principles contain no nitrogen. They are compounds of carbon, hydrogen, and oxygen, in which the two former elements abound. These bodies have lately been laboriously investigated by MM. Chevreul and Braconnot (Annales de Chimie, Tom. 88, 93, 94, and 95). The different kinds of fat are separable into two substances, one of which fuses at about $50^\circ$, the other at $105^\circ$. They may be separated from hogs-lard, for instance, by boiling in seven or eight times its weight of alcohol; the liquor is decanted, and fresh alcohol added, till the whole is dissolved. Each portion of alcohol deposits, on cooling, crystals of the least fusible substance; the other is obtained in the form of oil, by evaporating the mixed alcoholic solutions to one-eighth their original bulk. The reunion of these two principles produces the original fat. By exposing oils solidified by cold to pressure, they too afford a fluid and solid matter. The following are the relative proportions of oil and fat afforded by several of these substances:
| Oil | Fat | |-----|-----| | Butter made in summer | 60 | 40 | | Ditto made in winter | 37 | 63 | | Hogs-lard | 62 | 38 | | Beef marrow | 24 | 76 | | Mutton ditto | 74 | 26 | | Goose fat | 68 | 32 | | Duck's fat | 72 | 28 |
* Mr Hatchett's admirable Dissertations in the Phil. Trans. 1800 and 1799, contain a great body of information in this department of animal chemistry. The reader is also referred to Dr Bostock's papers i Nicholson's Journal, Vol. XI. and XIV. Turkey's fat, 74 26 Olive oil, 72 28 Almond oil, 76 24
The fat is fusible at different temperatures, and the fluid part of olive and almond oil requires a very low temperature for its solidification; so that it may perhaps prove very useful for watches and clocks. Chevreul calls the oily part elaine, from elain, oil, and the fat substance he terms stearine, from stear, suet.
When fat is acted upon by alkalies, it suffers a change by which it affords a peculiar substance of a pearly lustre, called by Chevreul margarine, and an oily matter. A sweet substance, a volatile, and an orange-coloured substance, are also produced. Margarine has acid properties, and exists in soap, as margarate of potash.
Brain and Nerves.
According to Vauquelin, the cerebral substance consists of:
| Substance | Quantity | |--------------------|----------| | Water | 80.00 | | White fatty matter | 4.53 | | Red fatty matter | 0.70 | | Albumen | 7.00 | | Osmazome | 1.12 | | Phosphorus | 1.50 | | Acids, salts, and sulphur | 5.15 |
The pulp of nerves seems to be of a similar nature.
Shell and Bone.
These may be considered as containing an animal substance or hardening matter. The animal substance in porcellaneous shells, and in the enamel of teeth, is gelatine; in mother of pearl shell, and in bone, it is a compound of gelatine and albumen; and, consequently, the former are entirely dissolved by dilute muriatic acid, while the latter leave a cartilaginous skeleton. The hardening principle of shell is generally carbonate of lime; in some crustacea and zoophites it is a mixture of carbonate and phosphate of lime; and in bone it consists of phosphate of lime, with a relatively small proportion of carbonate. (See Mr Hatchett's Papers, Phil. Trans. 1799 and 1800.)
Concretions.
Concretions occur in various parts of the animal body; they are often of the same composition as bone, as in the case of ossifications and exostoses.
Concretions of the gall-bladder, and biliary ducts, consist chiefly of a peculiar substance called adipocire, or cholesterine, combined with from 6 to 12 per cent. of the colouring matter of bile. Picromel, which is not found in healthy human bile, occasionally occurs in human biliary calculi. Gallstones sometimes contain a large quantity of the resin of bile, and sometimes appear to consist entirely of inspissated or thickened bile.
Urinary calculi vary considerably in their composition. The substances hitherto discovered in them are as follow:
- Uric acid. - Phosphat of lime. - Ammoniac-magnesian phosphate. - Oxalate of lime. - Cystic oxide.
These substances are generally more or less mixed in urinary calculi, and their different kinds may therefore be arranged as follow:
1. Uric calculus. 2. Bone earth calculus, consisting chiefly of phosphat of lime. 3. Ammoniac-magnesian, or triple phosphate. 4. Fusible calculus, consisting of a mixture of the two last. 5. Mulberry calculus, or oxalate of lime. 6. Cystic calculus, consisting of a peculiar substance, which Dr Wollaston has called cystic oxide. (See Phil. Trans. 1810.)
The properties of the four first calculi will be obvious from the preceding matter of this article. The calculus composed of oxalate of lime, when in the bladder, has much resemblance to a mulberry; when formed in the kidney, it often looks like a hemp-seed. Before the blow-pipe it affords quicklime. The cystic oxide is dissolved by muriatic, nitric, sulphuric, phosphoric, and oxalic acids; by potash, soda, ammonia, lime-water, and carbonates of soda and potash. Its combinations with the acids crystallize in slender needles; those with the alkalies in small grains. It is nearly insoluble in water, alcohol, acetic, tartaric, and citric acids, and in carbonate of ammonia.
The above substances, excepting cystic oxide, are often in alternate layers in calculi, and two or more are sometimes mixed so as not to be separable except by analysis. Urinary calculi have been found in the horse, composed of phosphate and carbonate of lime; in the ox, of carbonate of lime; in the dog, of a mixture of phosphate of lime and triple phosphate; in the hog, of carbonate of lime; in the rabbit, of phosphate and carbonate of lime. In the excrements of the Boa constrictor, and of some birds, uric acid is found. Independent of hair balls, calculi are sometimes found in the intestines of animals, composed of triple phosphate and phosphate of lime.
Gouty concretions consist of urate of soda.
Upon the subject of urinary calculi, the reader is referred to Dr Wollaston's Dissertations in the Philos. Trans. 1797—1810; to Mr Brande's papers in the same work; and to an Essay on the Chemical History and Medical Treatment of Calculous Disorders, by Alexander Marcat, M.D.
Animal Functions.
Under this head, the processes concerned in the productions of animal substances are considered in the article Chemistry in the body of the work. These processes may be considered under the heads Digestion, Transpiration, Respiration, and Secretion.
The food, masticated in the mouth, is mixed with Chemistry saliva, a fluid containing saline matter and albumen, and thus propelled into the stomach, where it becomes converted into a peculiar pulpy mass called chyme. This change appears principally dependent upon the gastric juice, which, by analysis, does not greatly differ from saliva, and yet produces very different effects. The nature of its action is not known. In the small intestines, the chyme is mixed with bile and pancreatic secretion; and hence chyle is formed, which, absorbed by the lacteals, and mixed with lymph, is carried into the venous system. Human chyle has not been examined: from the dog and cat it is a white fluid, of a slightly sweet taste, and coagulates soon after removal from its vessels. Its principal component part is albumen; and sometimes the serous part of chyle contains a body analogous to sugar of milk. The chyle of graminivorous animals is more transparent than the former, and nearly colourless; it coagulates spontaneously, and the coagulum is albuminous.
The matter which is transpired by the surface of the body consists of water, carbonic acid, acetic acid, phosphoric acid, muriate of soda, and a peculiar odorous animal matter. By the process of respiration, the blood is exposed to the action of air in the lungs. Having circulated throughout the body, it enters by the vena cava with the contents of the thoracic duct, into the right auricle of the heart; thence into the right ventricle, whence it is propelled through the lungs, and returns in the state of arterial blood to the left cavities of the heart, and is circulated as before. In the air expired, there is a deficiency of oxygen; instead of containing 21 per cent., it only affords 18 or 19; and there is a proportion of carbonic acid formed, exactly equivalent in volume to this deficiency. Aqueous vapour is also exhaled with the expired air. It appears, then, that the great end answered by respiration is the removal of carbon from the blood; it thus passes from the state of venous to arterial; it becomes fit for the nourishment, and reproduction of parts, and for the formation of secretions; and, while the parts of the body are continually removing by the absorbents, and the materials carried into the blood by the lymphatics, so they are constantly reproducing by the arteries, under the influence of the nervous system. It is probable that the colouring matter of blood remains always the same, and that in venous blood it is obscured by carbon, which, when removed by the air, exposes its brilliant tint, as seen in arterial blood, or in venous blood which has been exposed to oxygen. The nervous system seems to preside over secretion; for, when the nerves going to any gland are injured or divided, the secretion is modified either in quantity or quality; and, if it were possible to remove the nervous ramifications altogether, probably no secretion would take place. Animal heat is also the effect of the joint agency of the circulating and nervous system; for, when the great centre of nervous energy, the brain, is removed, there is no production of heat, though, under such circumstances, circulation may be kept up by artificially continued respiration, for a considerable period. Upon these subjects, however, which are rather physiological than chemical, we refer our readers to the researches of Sir E. Home (Phil. Trans. 1814), and to Mr Brodie's papers in the Philos. Trans. for the year 1811.
(M. M.)